I use both Cubase 7.5, PT11 and sometimes Logic X.
Cubase 7.5 is quite stable.
Performance (CPU, Latency) is comparable to Logic X and seems to deal better than PT11 with virtual instruments.
The only thing is that Cubase takes lots more time to load a session than Logic.
Even if Cubase still perform better on PC, It is not a major argument for me. I run really large orchestral sample libraries with lots of plugins without glitches and reasonable latency. I wouldn’t have switch to Cubase if I didn’t need better tools to work with Orchestral libraries (expression map, note exp, and more) and the new instrument tracks is really great.
What makes the most difference is the CPU power, Drive speed (SSD) and RAM. All DAW is performing great on my computer.