The vast majority of GTB thermal shutdowns that you see or read about are due to the motor temperature. The LRP speedos don't have a motor cutoff feature, so it is a good idea to have a temp-gun on-hand to make sure your motor stays in a safe temp range.
Novak has some bad press dating back to when all the motors had bonded rotors...the bonded rotors ran hotter and the GTB would shut down to protect the motor - but even though the ESC shut the system down, the magnets in the motor were still damaged, causing them to heat up faster and shut down even more often in later runs.
All in all, heat shouldn't really be a determinant in your decision - if you want a "LRP-spec" thermal shutdown feature, all you have to do is remove the blue wire from the sensor plug. I'm pretty sure this will void Novak's warranty for the motor...AFAIK, Novak supports the use of other brands of motors with their ESC, but they do not support the use of other ESC's with their motors (even though they work fine) - if a Novak motor is sent in with significant heat damage, Novak CS could easily make the determination that it wasn't used with their ESC.