The only con I know of with a hoop vs. floor frame is that you have to move it more often because you're working in a smaller space. But there are tons more pros! You can travel with it and quilt when you're out and about, you're not stuck in one spot in the house, you can rotate it in your lap and it's more comfortable, you can sit on any chair and quilt (or sofa, for that matter!), and the best part, IMO.... you get to be under the quilt while you are working on it.
Oh, one more con: it's a lot hotter to quilt in a hoop than a floor frame. So I plan on using floor frame in the summer!