In a word Zephiru79, someone has been telling you utter ****. The LAs are super easy tuners. They idle and transition like a dream and are every bit as reliable and long lasting as their ball raced capacity O.S. siblings. They're just not as powerful, but they're also about 25% lighter and a LOT cheaper, plus they burn less fuel per flight. A great beginner's engine, and certainly suitable for your first and second model.

An LA 46 puts out a claimed 1.2ps and the AX a claimed 1.65ps at peak power. That equates to the LA producing approximately 73% of the potential power of the AX if both were producing peak. No-one ordinarily operates them at that high an RPM in the power curve for sport flying, but the proportional reality IME is still somewhere around the LA producing approx ¾ of or 75% of the power of the AX in ordinary operation.

What does this all mean in practical terms for sport flying? Pretty simply, the AX will fly a bigger heavier model than an LA.

IME an AX will offer great vertical performance at 2.3kg, good vertical performance in a 2.5kg model, reasonable in an 2.7kg model, will kinda' still go vertical at 2.9kg, just, but struggle at anything above that. An LA will offer great vertical in a 2.0kg model, good vertical in a 2.2-2.3kg model, is still reasonable up to 2.5kg, but start to struggle above that.

With an LA, the engine itself is approx 100g lighter and you can get aways with carrying 8oz of fuel instead of 10oz if you want to saving another 50grams. Typical light good flying first low wing first tail dragger second ARF's in which an LA will perform very well would be a SIG Four Star 40, Great Planes Super Sporster MK II or my fav, The World Models Mfg Sky Raider Mach II. Stick an LA46, and 8oz tank and Bolly 10.5x6 or APC 11x5 on any of these and go ballistic. If it's only your second plane, the 46LA is a smarter choice and the perfect combo to maximise progress and have fun without breaking stuff. When your skills have developed to where you can handle the extra speed and power, simply space the bearers wider apart, then buy and bolt in your AX and go super ballistic.

Edited to remove foul language