Hi!
I have flown R/C for 30 years, competing in scale, pylonracing, sailplanes and aircombat and having flown helis for just pleasure and teaching newcomers in flying for at least 25 years...and I assure you that the best engine for a newcomer is the OS LA .40-.46 engine ...not the ballbearinged .40FX or .40AX.
The reason for this choice is very simple!
The LA engine doesn't have such temperament as the Ax or FX engines! And a temperamental engine that explodes in power when you give power to it is not what a total newcomer needs.
What he or she needs is an engine that produces good trust and is light in weight and responds to throttle action rapidly and without hesitation.
I know that all OS FX or AX engines are good at this too but they are much more temperamental in their behavior.
Using a 11x5 or 11x6 APC prop on a OS .40-46LA engine will give a very nice airplane behavior. Much better flight behavior than with a ballbearinged engine of the same size.


Then after a year or two when you have learned to fly and want a low winged airplane with a little more speed and want to do some maneuvers ..then get a ballbearinged engine.
But it doesn't have to be an OS....there are many more good engines out there.

Regards!
Jan K
Sweden