I just got through researching CB suites as I had originally thought I would book one for my upcoming trip. From what I can tell, these would be your closest options.
Castaway Building (Exterior Rooms) - 00-11, closest to the bus and central lobby / food court area.
Starlight Building (Exterior Rooms) - 00-15 next closest to central area, but slightly farther from bus.
As far as the interior rooms, I read where someone said they have a few family suites in Continental Building 00-21, but most of the interior rooms are all in the towers on the ends, so the farthest away from the central hotel area. Definitely confirm with Universal about these rooms, though, as I only saw one person report about them.
You can try requesting a room in one of the above buildings, but I'm not sure what your chances are of getting one.
As far as the hotels in general, I've stayed at both before, and they are both nice. CB has more of an exciting fun Disney-ish feel to me. The theming is great, and it makes me really feel like I am at Universal.
SF on the other hand just feels like staying at a very nice resort. It has more of an adult feel. I find it very nice and relaxing, and since I enjoy the walk and access to Royal Pacific, I prefer the location. I also prefer boats over buses. I try to avoid the City Walk security area and having to pass all the way through City Walk whenever possible.
I'm not sure the dynamics of your group or your plans, so it is hard to say which hotel would be the better fit. For instance, CB is great for trips where VB is a priority. It's like having a water park as your hotel's pool. I can also see it possibly being a better fit for families with kids who would appreciate and spend a lot of time in the lazy river.
On another note, will you be using a wheelchair or an ECV? Our first trip, one of our party had just had knee surgery, and was wheelchair bound, so we rented an ECV, and just pushing her around the portions where she had to switch to a wheelchair wore us out. Some of the ramps are quite steep. We found the boat was much easier to manage than the buses were, but that might not apply to smaller wheelchairs. It took forever to load the ECV onto buses. Whereas, it was a quick drive up the ramp for the boats. Plus, you then have to deal with elevators at Citywalk which you don't with the boats.
