Originally Posted by
syfi
Seeing as how your a/c compressor is spinning the same rpm, I'd say yes. They are running off the same belt! 
The rpm will depend on the diameter of the pulleys, if they are the same diameter they will rotate at the same rpm.
So what diameters are we talking about?
Under normal conditions the SC bearing will not be rotating at all as it will be locked up when the SC kicks in. So we can say that the AC bearing sees a harder set of conditions, side loads and higher rpm.