A couple of questions before I buy.

[Taqwus]

Bought both; SE4 before Dom before Dom II. SE4 was quite fun, but had some irritating quirks like bad pathfinding (ships burning all their movement points shuffling back and forth because a warp point was blocked by an enemy, say) and late-game micro (in particular, optimizing economy by switching to Monolith facilities was a serious pain, but made a potentially *huge* difference. Demolishing facilities to install atmosphere converters was repetitive). Good concepts, though, and very fun and varied ship designs -- I often had numerous different ship roles active simul e.g. heavy-gun/low-ROF ships, medium-gun/high-ROF ships, carriers, biowarfare, fast/armored transports, missile ships, etc and race design was also seriously nifty... and the modability's extreme. A little automation assistance would have gone a long way.
Dom II's quite fun, thematically pretty rich although it's not a plot-driven game in the sense of adventures/RPGs. Wackily high number of features, tools and methods allow varied viable playing styles; modding potential permits more. Learning curve may be a touch steep 'though as there's a lot to learn and a lot of knobs and twiddles have interacting effects.