You didn't mention powered or unpowered. You also didn't mentioned what "decent whitewater" means----the best way to be prepared for "decent" whitewater in a raft design is to have a raft with a self-bailing floor (inflatable floor that is laced to the pontoons, basically creating scuppers or drainage holes)
The up-side of a self-bailing floor is not only safety in big standing waves---it creates a nice stable floor to stand on for fishing. I had a "bucket boat" for many years (non-self-bailing ) They're reasonably safe (if you carry a bailing bucket) but they're not very stable to fish out of.
This is my current river ride--- an Avon Explorer with self-bailing floor. Fantastic river boat!
On my maiden voyage I dropped the anchor in Class III rapids (trying to sneak up on a springer hole). The anchor hooked into a crease in the bedrock below me and I was stuck going nowhere in a white water staircase. In a lesser boat, I would have stood a real good chance of swamping (from the stern going under against an immovable anchor). Things could have gone from bad to worse real quick, but the self-bailing floor kept things stable and I was finally able to get unstuck (and moments later hook the springer in the picture)
If you want power, there are lots of options to choose from. I have four rafts, all of different sizes that I use in rivers. They're all Avon Brand (UK made) The hypalon material that is used in the manufacture of Avons is not only incredibly durable but also easy to repair.
I have used these in rivers with up to Class IV rapids. I also use propellers (as opposed to jet pumps) because you can use much less horsepower (low weight) and get more torque at lower RPM's when pushing upstream (at a sane speed while staying on plane).
Here's the one I use on larger rivers and up to Class IV rapids (11 1/2 ft Avon + 15 Hp Yamaha w/ prop)
Here's the one I use on flat water rivers (up to Class III rapids) (10 ft Avon + 8 Hp Yamaha w/ prop)
I also get double use of this raft as a tender for my saltwater boat:
Pontoon boats---I steer clear. I have seen several of them flip in water a normal pontoon raft wouldn't have. One year I saw a guy in a pontoon boat on the Thompson in flat water (just above a Class III rapid) He leaned back in his seat and took a long pull on a beer, feeling on top of the world. The next minute a gust of wind flipped him over and he almost drowned going through the rapids. Too high a center of gravity for my taste
On the Kispiox this year I saw a guy flip a pontoon boat in a rapid that most guys in a normal raft design would have been able to read a newspaper while navigating. That same rapid gobbled up another pontoon boat about 5 years ago---to this day I still find bits and pieces of three nice Sage spey rods he was carrying when he flipped that boat.
