Wyomoose - I have an Avon 3.1m RibLite with 8hp Yamaha 2-stroke. The Zodiac Zoom you refer to and Bombard (SR I think?) are exactly the same boat and all three variants are made in the Bombard factory in France. The only difference with the Avon is that the tubes are hypalon whereas the other two are pvc, so you pay a premium for the Avon. I didn't mind paying extra because I use the boat purely for duck hunting in the winter on tidal estuaries and I needed the extra durability of hypalon. Didn't fancy having the tubes punctured by my dog's claws either!
The hull shape is exactly the same as the Zodiac/Avon SIBs i.e. a shallow 'V', although the extra rigidity of the hard floor in the RibLite does give them the handling edge over the fully inflatables. I've used mine in some pretty nasty conditions and it's coped admirably, but don't expect to stay completely dry. Obviously the hull shape means it doesn't cut through the waves, but rather skips and bounces over them which is fine, just makes it a more uncomfortable ride.
Both Zoom and RibLite are rated for 10hp, but they recommend an 8hp for less weight on the transom. Mine planes easily with an 8, with a dog, gun and large kit bag. It won't plane if there's two of us with two dogs, guns etc. I keep mine fully inflated on a trailer because getting it into that bag can be a pain. If you can be bothered with the bag, the boat folds up quite neatly and can be car topped. I've even had the whole boat inside a Range Rover and Volvo estate with the back seats folded down of course!
I notice Walker Bay has just brought out a 3.1m folding transom RIB, too. Check out their website, it looks more substantial than the Avon/Zodiac but costs a fair bit more I think.