My cataraft progression went like this....... started with a JPW 14 X 19 Flyer Cat, fast, agile, fun, but not much gear hauling ability for multi-day trips. Next came a 14 X 22 Maravia Cat, also fast & agile, but with a little more gear capacity. Now I have a 14 X 24 Maravia Cat and it's the perfect blend of size, agility & gear space for multi-day trips. I rarely carry passengers, I do mostly class III - IV multi-day trips, and I don't run class IV - V day trips.
I would say if you want to carry a light to moderate load and run big water, plus perhaps carry a passenger, then go for the 14 footer with either 22 or 24 in diameter tubes. If you just want a day play boat, go with either a 13 footer or a smaller diameter tube size 14 footer.
For me, my 14 X 24 Cat is perfect.