I've stayed in both and, while I like CBR fine, I have been back to CSR three times and am going back again in August. I love the Pepper Market and don't mind the 'mandatory tip.' Thinking about the conventions, I guess I wouldn't want to stay in the Casitas because they've always seemed a little louder to me as conventioneers sometimes seem to have get-togethers in their rooms, and they seems to generally stay in the Casitas (not that I blame them, I probably would to if I ever got to go to conferences...) so we've always been in the Cabanas or Ranchos. The spa is quite big, so when lots of little kids get in, as they frequently do, you don't get crowded out or get your book wet. There's also a big playground, which DS liked when he was younger, and the slide at the pool is neat. ALSO, if you go to the pool at night the lighting is pretty cool. Plus, there's a fairly big loop if you like to run, which is nice. Bus service isn't bad either, though I usually rent a car. I also like that it's not so 'super-Disney' as, say, AsMo, so you can get a mini-break from the Mouse, should you care to.
Reading this over, I guess there's no reason NOT to stay at CBR, I just like CSR better!
Have a great trip with DD! I'm taking my DS on a surprise trip in August and I can't wait!