The 31 was a great boat (1992.5 and newer). Does the 35 ride better? Yes it does. Those are two completely different hull designs. The 41 and the 42 Opens ride much better than the 35 and the 52 rides better than 41 and 42. See where I am going with this?
If you consistently run around in 3' chop or greater, I would highly recommend the 35 or 36 Open (built on the same hull). If however, you only occasionally see choppy conditions and a 31 is more in the size range you are comfortable with, you can't go wrong with a 31.
Ride has a lot to do with waterline length to beam ratio, hull entry, hull design and transom Deadrise. A 31 with a 10' beam would have ridden better than what Tiara built with a 12' beam, however my guess is that it would not have been near as popular. 2' less beam would have made the boat a much smaller boat. Everything is a compromise.
If you can go a bit bigger, for the money, the 35 Open is a better all around boat, but keep in mind that a 35 open is 40'8" long from tip to tip, so it is not really a 35' boat. The 31 for that matter is not really a 31' as it's LOA is 36'4" from the tip of the bow pulpit to the end of the swim platform.
The other issue is engines. If you want gas engines, I would stick with the 31. The 35 was a poor performer with gas. If you are going diesel, either boat is a good performing vessel.
If you want, e-mail me, and I will send you original buyers guides and performance sheets for the 31 and 35 (specify gas or diesel) in PDF format.
I sold Tiaras new for over 20 years, so I am very familiar with them. I have been to the Tiara factory about 20 times.
cburkard@burkardyachts.com
PS - The 32's ride is not really better than the 31. It is longer, but it is also wider. I would say their ride is comparable.