What is garage height, intended usage etc. I have a couple of reznors which are nice for moving air but radiant heaters are nice for keeping vehicles warm as well. If you are working in there in my opinion the forced air wins because it keeps a fairly uniform temp. However they are "windy" and noisy. Radiants are quiet but have slow recovery time and don't really distribute heat well except where they are pointed. (Should have a fan) In floor heat with forced air make up wins period.
My garage is 30'x36'x12'. I heat it wit a 75,000 btu Reznor. Aside from being a tad noisy on fire up, it works great. No cold spots in the shop at all.
Radiant tube heater works great and has all the same benefits of in floor but without all the hassles and recovery time is awesome. Doesn't blow dirt all around your shop like a furnace
I have reznors in two different garages. I like them good even heat throughout the garages. The one is 3 years old the other 2 i haven't had any issues with either of them.