i would say they sound different.... simply because they are different....

but how they sound and what sounds best is a matter of taste....

The difference would be mostly in the I/O your using in this case.
ProTools LE through a DIGI 002 RACK sounds THE SAME as SX running through the DIGI 002 using the CORE AUDIO driver

When I run SX through my MOTU828MKii, the same tracks sound just slightly different. More clear high mids noted. Not anything major BTW. I use both systems and the diff is MINIMAL. If you used an RME FW 800, then I would think the sound would be better on that system just because the converters and clock are better on that unit. Both SX and LE sound good.

i believe you are CORRECT shanabit. Im speaking of course from experience. Had digi 002r with PT and now have RME FF800 with cubase sx3.

The sound quality is better to me and the midi capabilities far out weigh pro tools. Cubase is such a good program. I recommend it highly.

thanks fellas