VX Ace is good in most of the things... it allows far more customization right away...
but if ur more into mapping, XP is deemed to be better...
but of course, if you can map using parallax method, then VX Ace would be better...
and on VX Ace, you can have the sideview battlers via Yanfly's Battle Engine + Visual battlers add-on, Yami's symphony engine, Victor's engine, tankentai
btw, you might wanna look at rpgmakerweb.com for more support with the makers...