I have never understood what's the difference between each version of Darkstalkers. All this talk about Savior and NW and Hunter confuses me. Please someone explain.
Vampire Hunter/Night Warriors is the same game. It's the second in the series. Hunter is the Japanese name for the game, but when it was released in the US and Europe it was retitled Night Warriors: Darkstalker's Revenge. It's worth noting that there are some minor differences between versions. NW fixed several bugs and glitches that were present in the original Japanese release of the game, and it also included some (but not many) balance tweaks. As a result, the tier list is slightly different between Hunter and NW. The Japanese don't play NW for this reason, which is why nobody really plays the game on GGPO, since NW is the supported version. In Japan, the original version of Hunter is still the competetive standard, while NW is the standard in the West. It should be noted though, that the difference between versions is very slight, and all combos and strategies for all characters should work in both Hunter and NW. This makes it easy to jump between both versions.
Vampire Savior is the third game in the series, and was released in the US and Europe as Darkstalkers 3. To the best of my knowledge, there is no difference between the Japanese and US/EU versions of the game, although Dev would probably know for sure.
The difference between Hunter and Savior is night and day. Both games are incredibly solid and hold up well in competitive play though, so it basically comes down to personal preference. Savior is more fast paced and technical, and to say it's rushdown oriented would be an understatement. Hunter is a little bit slower and doesn't require as much technical skill as Savior (although it is slightly more execution heavy than your average fighter), and it also has a stronger focus on defense. Basically, if you like fast paced, technical fighters that revolve around momentum and rushdown, then Savior is your game. If you enjoy games that are a little bit slower and have more of an emphasis on zoning and footsies/poking, then you'd probably enjoy Hunter more. There's also a difference in characters. Donovan, Pyron, and Phobos were all present in Hunter, but absent in the arcade release of Savior (which is the competitive standard). They were replaced with Jedah, Lilith, B.B. Hood, and Q. Bee. There are some more differences between the games as they relate to the game system itself, but you probably get the gist of it.
Sorry for the essay haha.