The width of the tire does not really matter for ride comfort. I think it might actually be the only part of the tire that has no effect on ride quality. The things that have effeect on ride quality as far as the tire itself is concerned are tire sidewall height, wheel height, thickness of the sidewall of the tire, type of rubber compound used and expected life of the compound (tire life), tread thickness and design, along with a few others I am probably forgetting.
On my previous vehicle I had Firestone 40,000 mile (195/55/16) on my car stock. They had great grip in the summer and the sidewalls were think enough not to roll too much, but they were a hard ride and they had horrible winter traction. I bought new tires after about 35,000 miles, Pirelli 3000s (205/55/16). They were slightly taller, thinner sidewall, and hard enough rubber compound to get an 80,000 mile warranty. They were a very comfortable ride, handled great in the winter and summer, and looked sharp because they were wider, but they rolled on the sidewall easier and were a little bit more noisy. After all was said and done with my accident that got me my new Mazda3, the suspension and the tires combined give me a better ride than either of the tire sets and suspension I had on my last car and these tires are Goodyear RSAs (205/50/17). I am not sure of the mileage warranty on them and they don't handle that great in the snow and ice, but comfortable ride with a good grip they can handle.
If you are looking for a tire that might be a different size than the stock and want to see what the new tires will do to your speedometer, I made a program when I was shopping for tires that let me compare two tire sizes and give data on the differences, sidewall height, diameter, circumference, and effect on your speedometer. I will try and get a download link for it or something up here.
Edit: I wonder if this will work to let you download it. It is zipped and virus free.
http://home.indy.rr.com/mnemonicj/Tire Size V2-03.zip