This is an easy one, from a lore perspective.
Vasari and TEC armor use a completely different tech base.
TEC armor is basically a highly advanced form of the composite armor used on main battle tanks today: a macro-composite containing a mixture of ceramics, plastics, and shock dispersal media, with some exotic components thrown in to deal with all kinds of nasty weapons systems.
On any given TEC vessel, you will have the following armor layers sandwiched together:
- Multiple polymer shells designed to deflect ballistic impacts and delay energy weapons
- A ceramic layer, designed to fracture and thereby absorb ballistic impacts
- A mesh layer, designed to flex and absorb ballistic impacts
- Alternatively, you could have ceramic plates in a mesh honeycomb, for fun and profit
- A liquid polymer layer, which acts as a shock absorbing medium and a sealant
- Several different foams, which diffuse energy weapons and absorb impacts
- An artificial crystal layer, designed to reflect beam weapons
- A frangible, powder, or liquid layer, the sole purpose of which is to throw up a cloud of particles to diffuse beam weapons (lasers and particle beams diffuse in atmosphere)
- A hard radiation absorber, lighter and denser than lead if possible
- An inner mesh designed to prevent spalling from kinetic impacts (i.e. your inner hull fracturing and turning into a hail of shrapnel when clunked by something big and heavy)
Install multiple iterations and combinations of this sort of thing, and the resulting composite will provide excellent levels of all-around defense per unit wight and per unit cost, both in terms of hard cash and in terms of resources (it's not particularly resource-intensive to produce). Unfortunately, it isn't something you can repair quickly and/or on the fly, without a series of specialized foundries, but it CAN be pre-assembled in modular slabs.
Got a damaged ship? Seal the infected area; pop out the damaged slab; roll a new slab out of the hold; pop it into place; replace your stock of slabs at the nearest port of call. Unfortunately, power-to-weight ratios limit the amount of spare slabs most ships can carry (and do you really want a Javelis hauling around extra armor when it can be hauling extra missiles instead?).
TEC repair bays, on the other hand, have the luxury of being in orbit around a population center that is constantly producing large quantities of the materials necessary for armor, and Hoshikos do little more than haul around armor slabs and the bots to send them out (fuel for the bots' antimatter torches tends to be more of an issue than the amount of armor slabs a Hoshiko can carry). I imagine that TEC repair bots do nothing more than run to a damaged ship and install new armor slabs, which is what allows them to repair their ships so quickly.
Note: different ship vulnerabilities can be based on the incorporation of different composite layers -- for example, Cobalts are obviously REALLY short on ballistic and refractive layers!
The Vasari are a different story.
Many substances require a long time and/or specific conditions to form. It can take hours in a lab, under tightly controlled circumstances, to manufacture even small amounts of certain materials. Vasari nanomachines are probably designed to automate this control component of materials design by responding reflexively to formative conditions; they will therefore continue to construct their designated products as long as they are fed raw materials, but that doesn't change the fact that the reactions they are instigating probably take a LONG time to finish and are VERY resource-intensive. Consequently, Vasari manufacture necessitates an infrastructure geared towards nano-engineering (in the same way that developing nations can't produce advanced microelectronics on their own -- they don't have the technology base).
But the product is worth the effort. Though perhaps less efficient than TEC armor in some ways (I wouldn't be surprised if the Vasari can produce only one superbly armored vessel for every two decently armored vessels the TEC produce), on a pound-for-pound basis, Vasari armor is more effective, more versatile, and lighter than anything the TEC can currently design.
Vasari armor (and if you look carefully at the Vasari Rebel tech tree, you'll note that Vasari armor was BADASS in its heyday) is entirely different than TEC armor. TEC armor is a macro-composite, combining different armor layers for synergistic effect at the macro level (the effect of each armor slab is greater than the sum of its parts). The whole package works because each specialized layer of that package performs a different function (shock absorptive layers, beam dispersal layers, etc). But the shock-absorbing layer can't diffuse a beam; the beam-diffusing layer can't absorb a shock.
By contrast, Vasari structural materials are nano-composites: their elementary components (such as individual armor scutes or even molecules in other structures) are engineered for synergistic effect. In other words, the synergy of Vasari materials occurs at the elementary level, not the macro level: even the most basic unit of Vasari structural materials, such as a scute, is capable of performing many (if not all) functions of a TEC armor slab containing multiple layers.
Vasari structural materials are probably divided by function:
- A skeleton, the elementary component of which is a solidified foam dispersed within a structural mesh. This foam-mesh composite combines flexibility with incredible tensile strength, capable of growing and repairing itself when "fed" the right raw materials. Overall, it is very much akin to human bone, constructed of advanced materials and including an integral resource distribution system for disseminating nutrients
- A meta-stable and damn near indestructible lattice that grows along nanomer wires and clings to the skeleton and inner decks like a net. The lattice itself is flexible, incredibly durable, and extremely light, as well as capable of circulating nanomachines, sealant chemicals, and other resources through the hull. It should be noted, however, that this lattice is not the armor, but rather is a structural element that contains the armor
- Plates of extraordinarily dense (but remarkably lightweight) interlocking nano-scutes. Each scute combines ALL of the traits of TEC composite armor in one package, equally capable of dispersing beams or absorbing impacts.
Here's how it would work:
- The skeleton is highly specialized: it is designed to respond well to G-forces and tidal stresses, not weapons fire. This is deliberate: if the skeleton skeleton were more resistant to weapons fire would increase its cost exponentially. Consequently: the limited functionality of the skeleton makes it easier and cheaper to build and repair.
- The lattice hardly ever needs to be repaired because it as close to indestructible as the Vasari engineers can make it. It's extremely expensive in terms of raw materials, construction time, and formative conditions. At a conservative estimate, 66% of ship construction time and resources are devoted to this lattice (even though it comprises less than 10% of the ship's mass), and field repairs are damn near impossible. It's also incredibly inefficient on a large scale, so Vasari engineers ONLY use it as a mesh, not as armor material proper.
- The armored nano-scutes, which are installed, layer by layer, into the lattice, are midway between the lattice and the skeleton in terms of efficiency and ability to be repaired. The scutes are tougher to repair than the skeleton, much cheaper and easier to repair than the lattice; but the scutes are far more resistant to damage than the skeleton (though not as invulnerable as the lattice). The scutes can be regrown in the field, over time, as nano-machines scale the armor lattice and install scutes at damaged sections.
As you direct fire onto a Vasari vessel, the armored nano-scutes go first, leaving behind a ragged lattice wrapped around a skeleton. As more fire is directed at the vessel, the skeleton collapses. Very heavy weapons, such as the Ragnarov's cannon, heavy beam cannon emplacements, or even the Kol's Gauss rail gun will twist, burn, or even sever the lattice, liberating and scattering armored scutes.
Advent armor is something of an oddity. The Advent favor shields over armor, and tend to focus their manufacturing on more powerful, precise, psychically augmented shield generators. They also view armor as a rather brutish, regrettably necessary contraption.
That said, the Advent are capable of psychically monitoring conventional chemical reactions via Psitech. Consequently, they are capable of approaching Vasari levels of engineering with a conventional tech base (that is, without investing in nano manufacturing). That said, this is an incredibly manpower-intensive process, and the Advent could not achieve Vasari levels of structural engineering without an extraordinary investment of menial psychics. As it is, Advent hulls tend to be macro-composites composed of multi-purpose components.
In other words: whereas each layer in TEC macro-composites serves a single purpose within the overall composite sandwich, each layer of Advent armor is sufficiently engineered that it can serve multiple purposes. Consequently, Advent armor tends to use fewer layers and is therefore lighter for the same amount of protection. That said: once again, the Advent typically invest in shields rather than hulls, so their ships tend to have much less protection than their TEC counterparts.
TEC: macro-composites composed of single-purpose layers
Vasari: nano-composites composed of multi-purpose elementary components
Advent: macro-composites composed of psychically engineered multi-purpose layers.