I had one of the ones that was supposed to use either 60 or 45 mm blades. It's headed for the trash as the blade will no longer stay down while you are using it (either size blade). Very disconcerting to be cutting and have the blade pop back up into safe position!
The 45mm blades are much more readily available so I'm going to just go with the 45mm one and the tiny one. I find I rarely use the tiny one though.