No, they dont. Surely you realize there is a bigger difference between black and white than between various shades of gray. If you do something better than someone else, it makes you less unique than if that someone cant do the same thing at all.
Until you fail to acknowledge this simple concept, its you who has a weak argument in this case.
Timmaigh, the speed at which an orkulus moves allows it to be properly micro'd to intercept a fleet. No other starbase will be able to do that nearly as good. So, in all reality, orkulus speed as it is currently would confer a "black and white" example of superiority. The vasari advantage would be that an upgraded vasari starbase would be like a "titan" with its ability to intercept a fleet if micro'd properly.
Using your argument in another sense, we could compare the advent's starfish to the ogrovs.
The ogrov is a better ship that shines, even though the advent also have a building destroyer of their own. One justifies the cost to build because it is a better buy for the cost. This is intentionally designed.
Using a real life example, using your logic:
If Arnold Schwarzenegger in his prime can lift something, and you can lift that same thing(no matter how heavy), then you and arnold are practically the same physically. lol.
HOW good something is at performing its purpose, and to what magnitude, is critical. After all, Arnold's "black and white" superiority to you would be that he'd win an iron man competition and win bodybuilding competitions. Yet you could still lift the same gallon of milk.
There are always shades of grey, and at the same time certain shades will be better for different tactical situations. Instead of having vasari be all black, and TeC and advent be all white, shades of grey would make it far more interesting, as long as those shades of grey confer to a direct tactical advantage for each shade.
So, with the Original post being implemented, here is how things would stand:
Vasari tactical advantage:
-Mobile heavily upgradable, heavy hitting starbase o' death. Nothing's changed. Best defensive starbase available.
TEC tactical advantage:
-Slow moving bombs, ability to set up gravity wells with surprise attacks. Using the "Red Button" would be more suspenseful for the player experience because they would be able to slowly inch towards their opponent. The suspense would build, and either the other player wouldn't react, or they would. Either way, you feel like you have a lot more tactical options at your disposal. Also, the TEC would have a lot more justification to use these starbases on the attack.
Advent tactical advantage:
-Ability to use their strong starbase abilities to a greater degree of efficacy. Advent starbases would be a lot more fearsome, and their cost would become justified. Also, Advent would have a lot more justification to use their starbases offensively(building in the enemy gravity well with fleet support).
Overall, more siege tactics become possible, opening up the game's paths to victory.
Each race would have their own effective version of the siege.
Giving every player the ability to do a strong siege is necessary, because the player experience of besieging a planet is a complex one. Many options, many choices to make. This equates to interesting gameplay for many of the sins target market.