Sonar is the only current Cakewalk product that supports SMPTE. I have HS2002 and it does support MTC and external clock sources - don't know about GS2002.
If in doubt, just buy HS2002 ($70) - it is the most feature filled Cakewalk product after Sonar. If you really need SMPTE, you're gonna have to dish out the $300-400 for Sonar.