I started with a Buck's Bags 8 footer. I used it on lakes and the Stilly, both the main and north fork. It was ok but I needed to go bigger. I'm not exactly small and I didn't like having half the tube under water. What it boiled down to was that I wanted something I felt safe taking down bigger water. I now have a 10' Xstream cataraft. It handles better, I can stand on it, it anchors safely (within reason), and it has more room for gear. It just feels more stable overall. The trade off is that with the bigger models you can't just pick it up with one hand and carry it down a trail to the river. My Buck's weighed somewhere around 40lbs which was no problem to tote around. My Xstream is closer to 100lbs.
The Xstreams and Bad Cats are very similar and are both around a grand.
I don't mind paying a few hundred dollars more for something that I'm trusting my life to.