I'd say stick with XP or go with MV. If you stick with XP and have some dollars to spare, you might want to buy VxAce on sale just for a license to use the RTP and RTP edits since they can easily be converted. but VxAce really, as an engine, really isn't that superior to XP.
If you're somewhat serious about making a game and sharing it with more than your friends though, I'd still advise you go with MV. Because that engine IS superior to both XP and Ace. Stuff like being able to zoom in and out just by using the scroll wheel on your mouse (which is expected today) makes a big difference when making your game and speeds up the overall development.
Also the scripts (called plugins) are really plug-n-play (mostly) and much easier than what you ca get for XP or VxAce, usually more powerful too.
For example, if I remember correctly there's a lot of problems with changing the resolution in XP and Ace, even with scripts. In MV it's super easy and that's just one of those small things which you don't think a lot about but it makes a big difference. Because everyone expects the game to fill out the screen and not open in a window when they play a game today.
In summary, once you go MV, you don't go back!