What's the most powerful Veritech and why?

The best I can think of (if you mean a Veritech fighter) is probably the AGAC because it packed many powerful weapon systems like it's dual beam cannons and it's Scatter Pack Missles that could heavly damage a Tirolian Dropship and accounted for many, many Bioroid kills.

I second. AGACS are the ultimate space combat fighter.

I thought you'd say as much. I dont see the REF having a good day with just those Alpha fighters aginst the might of the Tirolian Empire (theoretically, of course)

I am torn between the Vindicator, the YF-19 and the YF-21, and the Beta Fighter.

Vindicator- Pros: Zentradi size, first generation fusion (not shadow) reactor, destabilizer gun w/ 2 clips (I think), 70 missles
Cons: Cannot escape the atmosphere under its own power.

Beta Fighter-Pros: Big brawling size with arm shields, atmospheric capable, multiple ranged missiles, gattling gun centrally located with larger than normal ammo store.
Cons: Big target, Protoculture range and target, if shadow equipped even bigger target

YF-19 and 21- Pros: Multiple weapons pods that can be jettisoned, capable of folding if only once, YF-21 is mind controlled, they both appear to capable of atmospheric flight alone, I hope post shadow stealth technology.

So my vote, YF-19 or 21.