I have found both engines to be very user friendly, very dependable (I have two OS46's with more then 400 tanks of fuel through each of them!) and quite powerful. The main difference has been that of power between the two. And once both are set up optimally they both will give more then enough power for even the heavier 50 size heli (of course with the 50 having a slight advantage)

1) OS-46FXH - This engine got a "bum" rap when it was released because it was released into a market that did not understand the requirements of a heli 46 engine
a) They need a different exhaust system then that of a 40 or 32 and many where trying to run them with one of these "older" generation mufflers.(Note:Some of these were even inadequate for the higher output OS-32SXH!)
b) They need an appropriate load and gear ratio to run properly. Many people installed them in helicopters that were using mainblades that were too short and with helicopters that had gear ratios designed for use with the 32 size engines.
c) They were installed in some heli's that also had the head pointed at a downward angle instead of the standard forward or back. This would cause them to load in the idle if set properly in the midrange.

Some were even installed in helis that had points a,b and c working against them! Of course, a lot of these uninformed owners were quick to spread the word that these engines were crap on the net and whenever they would talk to others.

2) OS50SXH - This was released into a market that had already learned the lessons of a,b & c above. Obviously it would not have to suffer the same fate.

I and many around me have always had great running OS-46's. Why? Because we all only fly helis that have the proper gear ratios (Mystar 46, Falcons and the odd GPH), used 600mm blades instead of shorter 30 size blades (570, 560, 550 or some 46 heli's even came with 530 blades!!!) and used appropriate mufflers (KS-468's and CN3033A's - Note: nobody here has tried the CN3033B yet so I cannot comment).

At last count there where more then 32 OS46FXH's in helis around here (mostly in Falcons) and all running very well!