HHT is the best gauge initially( and you will eventually alos be able to discern different levels of HHT sharpness: popping hairs, cutting hairs, silently severing hairs...), but as has been said the real test is on your face.

Sometimes a razor will HHT OK, but will leave you with stubble on your face, that razor needs a bit of a bevel re-set probably (could be other factors as well, of course...)

Anyhow, sounds like you're off to a great start! And yes, a straight will always present a bit more resistance as the blade is significantly longer.