Cubase for Mac is very stable, but there are things which will render it unstable. High up on the list of these is 3rd party plugins. The only thing that ever causes C7.5 to crash on my Mac is Autotune 7.
As a start try removing all 3rd party plugs, then put them back and see when the problem returns.
Trashing prefs, and/or a fresh install often helps, as does a clean and lean install of OSX.
Do a search here, there is lots of advice for instability problems on both platforms.
Just because another user reports instability, doesn’t mean the whole thing is unusable.
Post your system specs, you are more likely to get helpful advice.