I would go with the iPad simply as there is a far bigger range of apps and games to use. (Plus I'm biased as all my music is in iTunes.)
iTunes is horrid, it's one reason why I would chose the Surface. You just need to be able to drag and drop to devices. The Surface needs time to mature but the hardware looks awesome.
On OSX/iOS it's brilliant I recon. Since day 1 of it been released I can't say I have had an issue at all.