Just to add my two pence....
I don't think any small fast boat is particularly soft. If you want a softer ride then you probably need boat that either pierces the water, (I seem to remember there was something about new wave piercing RIBS somewhere) or a slow displacement vessel thatís glued to it. If you're going to jump waves fast then at some stage it will hurt!
The tubes may soften some wave impacts but gtflash, don't expect magic from them. Some RIBS are much better than others as far as softer rides go but that's more down to the design/shape and particularly length of the hull.... As usual the longer the better!
To my mind the reason RIBs are called the 4x4 of the sea is that they are bloody hard to sink. Its the only type of boat that is short enough to fit in my front garden, I can tow anywhere, manhandle on the trailer AND if it blows up a force 6 or more I will still feel safe.... (If bruised battered and pi***d off). The main effect of the tube is safety through a fantastic amount of buoyancy, not necessarily a softer ride.
To my mind, you will need a much bigger 'ordinary' boat to be as seaworthy... not necessarily to be softer. Ask Ageing Youth!
As someone said earlier, the last thing you buy a land rover for is a smooth ride!