The Space Empires games are targeted somewhat differently than GalCiv2. They're aimed a bit more at "control and detail freaks" (of which I include myself as a part-timer). For example, GalCiv2 has its feature set carefully managed. The feature list is kept manageable for a variety of reasons: a) accessibility,

balance, c) AI competence. The result is a streamlined, well balanced game, with an AI that can kick my butt on a regular basis.
Space Empires goes the other route - the one of "featuritis" (that's not a criticism, just an observation). It's difficult to find things that AREN'T included in Space Empires games. For example, all of the following things are present in SEV:
- Fighters and carriers.
- Mines.
- Armed satellites.
- Unmanned drones.
- Ground units.
- Planetary weapons platforms.
- Extremely detailed ship design. There are tons of special purpose components you can research (even turnings ships into mobile ship construction yards, mobile mining platforms, etc.).
- Ship ramming (and the ability to design ships with suicide warheads in them, if that's your thing).
- Bizarre weapons like tractor beams, repulsors, engine-overloading weapons, computer viruses, etc.
- Detailed design (as detailed as ship design itself) for all of the fighters/mines/satellites/drones/units/platforms mentioned above. There are even 3 hull sizes of each.
- Tactical space and ground combat (previously turn/grid based, now in real-time for Space Empires V).
- Ship capture.
- Cloaking ships (and ships designed to detect cloaking ships).
- Planetary invasion.
- WMDs (researching Stellar Manipulation ultimately lets you create/destroy planets, stars, black holes, and warp points).
- Conquering and ruling of alien races (with planetary populations thus composed of racial mixes).
- An "infinite" tech tree (there are something like 6000 tech levels that can be researched - you'll never do them all in any single game).
- Race-specific branches of the technology tree, like organic, crystalline, psychic, temporal and religious technologies.
- Extremely detailed espionage.
- Diplomatic treaties that can get incredibly detailed. Here are just some of the more unusual items that can be included in treaties: 1) One or both empires is prohibited from making treaties with anyone else, 2) One or both empires is prohibited from performing things such as: planetary bombardment, viral weapons, planetary destruction, solar destruction, black hole creation, nebula creation, ship cloaking, 3) Empires will share intelligence operations, including reports on enemy ship designs, etc.
- Extremely moddable.
Of course all of this comes at a price - and a pretty hefty price at that...
- With all of the above detail, there are pages and pages of information to digest when running your empire. This has earned it the derogatory nickname Space Spreadsheets.
- The interface has always been somewhat of a... challenge... to use.
- It's impossible to have all these features as well-balanced as a game like GalCiv2
- The AI has no hope of getting its head wrapped around all this, and just has to blunder its way through things.
- Also, the development "team" on it is basically just one person, plus a few associated artists, modellers, etc. As a result, the polish quality of it isn't what something like Stardock can manage. The post-release support is extremely good though.
One aspect I'm looking to try out with SEV is multiplayer. It can be played not only via network "live" but also PBEM. I have fond memories of playing VGAPlanets and Stars PBEM games, and I want to try one with SEV. That way you can play against humans, and get involved in all sorts of diplomacy, etc.
Anyway, I'm a fan of both GalCiv2 and Space Empires. I'd hate to have to give up either. SE is definitely not everyone's cup of tea though.
-Cauldyth