Crystal Space is actually trying to be everything. FPS, sim, Isometric. Which, is good and bad.
I've not seen this Vegastrike, what's the source code look like? Is it easy to compile a working exe? Does it have working netcode? Documentation is key (especially to Daves point about spending more time figuring the engine out than it would take to code one from scratch. You may disagree with him on some things, but the point is valid). How quickly can we have a single custom ship, under player control, in an exe for other people to look at?
A general caution on quality: a GREAT engine can look bad because it still uses programmer art to demonstrate it. My TQ project has got some REAL dog models, badly texture mapped, badly modelled or both. That doesn't mean the engine can't deal with them, just means that I suck at art

Good homework, though, we probably need a score card so we can honestly evaluate the choices based on the same criteria.
Thoughts?