I too prefer the 60mm self closing Olfa...I really, really like that it closes the blade when you stop squeezing. That has always seemed far safer to me than a blade you have to purposely click "closed".

Safety is the biggest issue I have with the martelli. Yes, there's a cover, but you have to remember to close it every time. But the worst thing is, when I go to set it on the table (between cuts) it often goes blade-up. I've cut myself (only once so far) on the sticking-up blade. So you have to consciously set it blade down between cuts (it's easy to set it the wrong way) or remember to close the blade every time.