In a Maria Shell class she urged us to try the 60 cm and I love it. The one caveat I have on all rotary cutters is make it one that shuts the blade automatically, as soon as you take your hand off it, ie. the Olfa Ergonomic cutters.
I think it is dangerous to have the models you must purposefully click to the closed/safe position...one day you are going to forget and that exposed blade will get you!