Nah they may be different but they're still all the same, only difference is hair models and body build for the guys. Dimensions uses the same modified version models of the 2U models(You can tell since Kasumi and Leifang and a few others use their old 2U hair modelsl and it uses the DOA4 models for the new characters but downgraded like Kokoro has her hair tied and Lisa looks worse and Eliot looks almost different.Actually, I remember reading on Hardcore Gaming 101 that 2/2H, 3, 2U and 4 curiously all use different models. Mind you, similar looking, but different.
Games prior to DOA5 that share models apparently are 2U and Xtreme 1, and then 4 and Xtreme 2.
A comparison with HQ screens would be apt for this research though, lol.
(Even in DOAD they made new models, I think. )
My only issue with the realistic style in 5 was the shoddy modeling of some things, the mistreatment of dudes, the dull colors, and looking back on it... Well, not much else, I think.
I think they took inspiration from Omega Force's games, and it wouldn't surprise me if the teams shared artists. Though I wish they took the extra step to make it look a tad more anime like Samurai Warriors does.
I don't want an anime look for DOA6 but I still say they should make the game look more like Dissidia FF NT, it's the best looking game art style and design wise imo. It looks realistic while still keeping a manga like approach similar to the original FF designs