Surprisingly AS5 Still holds its own... after its extremely long curing time. Much better though to go with something modern that requires little to no curing.
A well applied paste is much more effective than an an expensive one.
The oldschool p4 I use at my shop actually has hedgetrimmer gearbox lube (essentially lithium grease) as a thermal paste. Been 3 years now. Dont give 2 craps about the temps. Works just fine