I'm a visual person, so the health bars are fine with me. They give me a better idea of how much health something has, whereas numbers mean nothing to me. In Emerald though, if you press start in a double battle, your Pokemon's health appears in numbers. If that could be an optional feature, then that'd be fine. But I think at this point, the health bar is a staple in the series.
As for numbers actually showing up when a Pokemon is damaged, again, it's like a staple in the series now. It'd be odd to suddenly change it and have damage show up like that.