Vita, while cheaper and portable has two major flaws.
1) Frequent frame rate loss down below 15fps, especially when there are horses on screen. Considering the amount of battles with cavalry, thats not good
.
2) Only a few enemies on screen at a time. The game acts as if enemies who aren't being rendered don't exist, so attacks that should kill more enemies only kill a few. Additionally, bosses will often not spawn in until AFTER you've passed them. Considering What Warriors Orochi 2 PSP managed to do with weaker hardware, and the fact that enemies will be visible across the map in DW8 vita, this is pretty inexcusable.
If they can increase the enemies on screen, it'll be acceptable, but at this point it feels like they put very little effort into it.
Also the character models look PS2ish.