Vampire Savior/Hunter 2 had gameplay tweaks mostly (the only one I remember offhand is that Bullettas autocombo super, hcf+KK I think, comes out slower). Maybe also new alternate colors for the characters, and a different ending (or endings were just accessed differently, I could never get the "normal" character ending, only the one where Bulletta poses).
The Dreamcast version had those as selectable game rules, both Hunter 2 and Savior 2. It also included all other Darkstalkers game in one pack by the way.
Later re-re-rereleases of that DC pack probably have retained these options.
The Saturn version of Vampira Savior doesnt have any of the Savior 2 rules, minus Donovan, Pyron and Phobos being selectable by default (they werent in Savior 1 arcade originally, Savior 2 added them and switched out 3 other characters). I haven't played the psx version of Saviour a.k.a. Darkstalkers 3, it may have included more rulesets including savior/hunter 2.