Well the os .46fx is great and very reliable but IMO I too think the TT pro .46 is better. One reason its 30 dollars cheaper! the TT. pro 46 is harder to break in, but every run it gets stronger and stronger.

The os 46 fx has Horsepower: 1.62 BHP at 16,000 rpm Weight: 13.2 oz, 16.45 oz w/muflr .

The tt pro 46 has Power Output: 1.43 at 16,000, Weight (w/muffler): 17.01oz (482g)

I am going to use the tt. 46 with macs pretuned pipe on my next fun fly, morris topcap. Though they really are both awsome engines.