Not that I'm excusing the devs sloppy job, but there are AI mods for SEV that supposedly make it much better. I'd also suggest finding some sort of balance mod before playing it, as by default, the starting technologies feel most effective and the newer ones are practically just for style, at least with the default AI, which I never had troubles destroying with fighter swarms and they never even got to technologies which could make depleted-uranium weaponry ineffective.
Despite its short-comings, it's my favourite 4x game to date. It's got tactical space battles, tactical land battles, ships/units can have components disabled during battle, they can be captured, etc..
Not mentioned here yet, there's also a great 4x game called Emperor of the Fading Suns, which sort of plays like Panzer General (with stacking, diplomacy and resources) on land, sea and space in a WH40k/Dune sort of setting (zealous view on religion and great houses competing with eachother).
If you want it simpler than either and don't mind a few things that don't quite make sense (like having to research planetary invasion :|), then maybe you should try GalCiv2 (
demo available), which sort of plays like a Civ4 in space.