I'm not sure if you're asking if I'd rather paint the wall (as opposed to wallpapering it), of if I was definitely going to paint the wall and opt to NOT remove the wallpaper.
I happen to like paint. It's easier for me to maintain a damaged-and-painted wall than it is a damaged-and-wallpapered wall. We use wallpaper/border up towards the ceiling to add any 'flair' to the room. Bathrooms and kid rooms especially.
So, for me at least, before I say the wrong thing or too much (which I usually do but not on Monday mornings), what would YOU like to do? And what rooms are you working with? Why would you be swayed one way or the other???