I only played the demo of SEV for a little while, and the impression I got was that it was a very big game with lots of "stuff" in it, but it was also micromanagey, repetitive, unbalanced, and the AI was weak. If you play GC2 at gigantic/abundant and wish the game was bigger and longer, then you might like SEV, but it didn't appeal to me at all.
What
nullspace said. I too played the SEV demo, and I was almost overwhelmed by the sheer amount of stuff in it -- there's so many buildings, techs, ship componenents, etc., that I admittedly found the prospect of having to try to make decisions about what to build/design/research to be pretty daunting. While I realize that such a plethora of goodies to play with probably appeals to quite a few strategy gamers, it was simply a bit too much for me.
I much prefer GalCiv's more streamlined tech tree and build list. It's deep and complex enough to be satisfying, but not so much so that I become buried under an avalanche of minutae. In addition, I second what
Zyxpsilon said about Stardock providing both a more complete (i.e., bug-free) product, as well as superior support & service after that fact. Even after four years, I continue to be astonished at the committment Brad & Co. have given to both their games & their fans -- both in terms of post-release work, as well as the access we have to their persons -- and I suspect I will continue to be so in the future.