[Taqwus]

I played SE IV (original Version, not Gold). I find that quite different from Dom II. For instance...

...SE IV has a much more detailed economic/industrial model. Worlds have facilities, and certain technologies let you get FAR more out of them than you would otherwise (Atmosphere Converters, System Computers come to mind) so there's much more to optimize. In addition, building it all up is expensive, so the loss of a world can be quite a setback -- especially if the attacker decides to turn a highly-developed world into an asteroid field. There's more micromanagement because of the level of detail. Dom II has far less building (every province can have a temple, lab, castle; and tax rate can be set. That's it) and tends towards global population -decline- (slow growth rate, random events that cause pop decline, spells that kill pop, sacrifice of pop, dominions that kill pop).

Individual units in SE IV are far more robust than Dom II. Many units in Dom II can be reasonably expected to die in mass, and can often be replenished very quickly. The use of magical transport means that reinforcements can be moved up pretty rapidly. Conversely, SE IV ships operate on a comparatively larger map, in fewer numbers, with slower reinforcement (and while warp-point generators are possible, they're expensive and rather advanced tech) so there's a greater need to keep them intact. Repair ships become quite important, and supply is critical; in Dom II, being out of supply means a risk of starvation, while in SE IV being out of supply prevents movement and firing.

SE IV has a greater transition between a decent possibility of turtling (minefields, weapons platforms, combat satellites, choke points; compare to weak Dom II province defense) to the eventual Hammer of God technology (ability to generate own warp links giving insane mobility past even deep defenses, ability to detonate stars wiping out all ships and planets in the system, ability to smash planets) which guarantees that stalemates are remarkably unlikely to be permanent. Dom II tends to reward offense and growth, but it's harder to pull off the extreme scorched-worlds policy that SE IV lets you eventually do. A raid can smash a temple if there's no castle protecting it, but to ruin a province takes more doing, while the destruction of an entire star system and the sixteen worlds that you meticulously constructed out of asteroids can eventually be done with alarming speed.

SE IV has no equivalent to the concept of Dominion; possession is everything. In Dom II, you have to worry about religious influences, in that even conquest of a province doesn't mean you've changed its belief system. And if your pretender is no longer worshipped anywhere, you die, regardless of how powerful your armies are.

Dom II magical sites can make certain provinces more valuable than others, and there's a heavy element of luck in this. A site that makes blood magic 40% cheaper to use, for instance, makes that province VERY valuable for certain nations. Choke points are relatively few in most maps, and it's easier to bypass them (flight, magic, stealthy armies) than in SE IV (until very late in SE IV).

Dom II races tend to differ more, with different selections of national units. OTOH, they're less customizable, which means that they may be more predictable. SE IV races generally have a broader range of possibilities (access to a large variety of technologies, including the special tech trees you pay points for) and can therefore use a wider range of unit classes (carriers, mine ships, biowarfare ships, capture ships, missile ships, heavy-beam ships {heavy beams firing occasionally}, fast-beam ships {lighter beams fire every turn}, dedicated PD ships, planetary assault {speed, shields, bombs, cargo space for troops}, warp-link ships, planet-smashers, star-smashers, recon ships/satellites, killer satellites, supply ships, repair/construction ships, etc) which leads to less potential predictability. If you research it, you can try to build it, whereas in Dom II in any one game you'll probably research many spells that it's not practical that you'll ever use because of a lack of mages strong in the relevant prerequisites. You don't expect Abysia to slam you with lots of lightning/air spells, for instance, nor for Ulm to make heavy use of death magic, or Atlantis to rain Flames from the Sky upon you.

Dom II has far more limited in-built diplomacy. AIs don't trade, for instance, or warn you away from border provinces, or make treaties. However, in MP, the relative difficulty of defending it all (weak defenses, difficulty countering all likely attack forms everywhere) and the general specialization of national mages (making it harder for one side to build all the items that would be useful for it) encourage diplomacy among humans. Treaties/NAPs make sense, as does item trading.