Quote Originally Posted by lilimike View Post
If power is not an issue then I could use the fastest crystal supported by the PIC and it wouldn't cause an issue?
In general yes.
A chip running a 4Mhz will have a different resolution for the commands than say a 20MHz:
COUNT
PULSIN
PULSOUT
PWM
and maybe others I am not thinking about. So if you need a wider resolution then a slower OSC will be needed.

But in general, crank it up!!! It does not hurt the chip.