Greetings,
Beeing a SE IV (and modder), SE V Beta and GALCIV player I think I can give my 2 cents:
- SE V has a looooooot of dept. The learning curve will be very steep for a non SE IV player. It is not the combat rock/scisor/paper type galciv has. You have mines, satellites, tons of weapons, shields, armors, cloaks, fighters, carriers, formations, experience to deal with.
- SE V does not have the nice look and feel of Galciv. Don't even think it comes close.
- SE V universe is based on warp points. You hold a few choke points and manoeuver with choke points in mind.
- SE V does not have influence.
- SE V starbases are really starbases around planets, in sectors or defending warpoints.
- SE V does not have the same emphasis on dealing/diplomacy. There is diplomacy, but it is not as important than in galciv.
- SE V has tactical and strategic combat. Galciv combat is a little bit like the SE V strategic combat.
- SE V has modding capabilities that are simply incredible. However, Galciv modding capabilities are quite nice.
- SE V can built ships on planets, in other ships or starbases when you equip them with space yards.
- SE V, when you invade a planet of another race, you get the ability of that race on that planet and you can move those people to other planets to transport the ability. For example, you invade a gas based race and you are rock base race. You can move those people to any gas planet and you don't have the penalty.
- SE V support ships are very important.
I am still playing SE IV after more than 2 years of play because of that complexity. galciv is great, but after a while you experienced every gameplay you could have. In SE V, you can play defensive (mine warp points), you can play very offensive (use all ships type and fighters or play economically. technology is VERY important in SE V. If your ship is equiped with a defense combat sensor and the enemy has not a combat support computer, he will get wipped by you because he can't hit you.
Don't get me wrong. Galciv is a great game. The programmers simply put their energy on different things than Space Empire. One last thing: Galciv support and presence by the development team is a lot superior of what I saw with SE IV. the like-those-guys factor is a lot higher with galciv than SE.

Thank you