Its true that Advent have superior shields. Its also true they have fragile ships. Bypassing the shields (phase missiles for an example) will make them die quickly.
Whilst it is true there are some area energy weapon enhancers (Mothership malice, Halycon energy weapon aura) go extremely well with those Illuminators the focus shifted somewhat from LRF (long range frigate) warfare twoards strikecraft (fighters/bombers).
And Tec has the Marzada. Behold its terror! Not only is it featuring the barrage of area death (its not enhancing damage of the fleet per se, its more taking down fleets by itself) its also a the best planet killer in the game. I see little difference between enhancing energy weapons of LRF fleets and dealing AOE (area of effect) of death, save that the first needs a fleet and the latter can accomplish it alone. Of course even a Marzada will be shot down alone, so you need kinda a fleet also (albeit early in the game you will ANNIHILATE colonies with a single Marzada).
Its different but i do not see severe advantages or disadvantages for one side, except one: the Marzada completely eliminates the need for planet killing abilities. Just one is enough to kill a planet in no time. Thats a slight advantage for TEC.
If you compare Guardians to Hoshikos the Guardian is the better craft, because of their "push" ability. But Hoshikos repair even near dead capital ships in no time, the Guardian shield extention is a little different, keeps large amount of craft better protected but will not prevent a capital kill as good as Hoschikos.
This is only true for the beta patch however, without it Marzada will not be able to perform missile barrages accordingly and Guardians and Subverters are even more powerful (and can be bug abused).
So yeah, TEC is weak without the beta patch. Not unplayable but you will fight under some disadvantage (RA *shudder*). Get the patch. Seriously.