I have a VisTablet Realm and I love it. But, I did have to set aside quite a bit of money to get it. If you want something affordable, I'd stick with the VisTablet line. It's not as solid as Wacom, but it's always been a reliable brand for me. Then again, if you do want to get the extra features, pen sensitivity, and quality in make (which is totally worth it) than Wacom is your way to go. Mostly what you'd be sacrificing is size.
I really like what I saw from VT, but the deal breaker is that it doesn't bundle any software with it like Wacom does. Wacom offers to include Autodesk Sketchbook Express and Artrage Studio with their Intuos Pen, but I'm not entirely sure how good those programs are to begin with.