The FX is definately the strong, quality, engine.
The LA is a very reliable, but weak engine.
BUT if the LA is put in a plane like a light traniner it is a great combo. I built an LT-25 which weighs only 4.5 lbs. and put my old .40 LA in it. I fly low wings with Saitos but I will always have a trainer. I built this with almost no dihedral. I had 150 flights on that old engine in a "rebuilt-several-times" Superstar!!
It was sluggish to say the least. Now in this LT-25, (63" span), I have near unlimited vertical!!!! ...lownslo..
Bob