ORIGINAL: Eagle Al
The OS 46 LA and OS 46 AX are apples and oranges. The LA is a modest hp bushing engine that should be ideal for your application. A better choice might be the 40 LA which is slightly less HP, is a few dollars cheaper, but has the same external dimensions.
The AX is a powerful double ball bearing engine that better belongs on a high performance sport plane. Besides more HP, it's more money and weight. I have both engines, and I would recommend the LA as the best choice considering you want to practive TOs and Landings on a simple trainer. Beginners often make the mistake of putting too much power on their models which really defeats the purpose of training or learning basic things.
Ciao,
Eagle Al
The LA40 is also heavier than the more powerful LA46 but neither has the power of a ball bearing 40/46. Why is it heavier? It has a thicker cylinder liner. Both have the same crankshaft (stroke) and case but the 46 has a larger bore (piston) which means the brass liner is thinner. Less weight, more power!