The FX is an ABC engine (Aluminum piston in a Chrome plated Bronze sleeve) with the crank riding on ball bearings. The LA series are non ABC bushed engines. There's no comparison in power and performance, the FX wins hands down.

Be very careful with the Sportster. It will fly nothing like a small electric. It will be about 10 times as fast, and will cover about 20 times as much space (in half the time). Lose orientation for a second or two and it's history, unlike a slow flying more forgiving electric.

You also don't want to go back to your parents and say, "You know that plane I whined about for weeks? Well I just turned it into a pile of sticks." [&:]

Get an instructor.
Dennis-