ABX just means either Aluminum/Bronze/Chrome (ABC) or Aluminum/Bronze/Nickel means the engine has an Aluminum Piston, a Bronze sleeve, and either a Chrome or Nickel plating on the sleeve. This results in differential expansion of the piston and cylinder sleeve that causes the cylinder sleeve to expand more than the piston. The result is an engine that fits very tight when cold, has a low friction fit when hot, and tends to loose compression and stall if it overheats on a lean run. The other option for the cylinder and sleeve is a cast iron piston with a ring. This is more like the classic engine. The ring seals the piston.

ABC/ABN engines are cheaper to mass produce, but the parts will wear out quicker. Ringed engines take more machining, but will last longer.

As far a performance, with todays engineering, I don't think there is a huge performance difference.

As for Ball Bearing vs Bushing, now you're talking about the crankshaft support. A Bushing engine is lighter and cheaper to produce, but the bushing is by nature a higher friction part. A Ball Bearing requires more weight, but significantly reduces the friction lost in the crank. Consequently, equivalent size Ball Bearing engines (BB) will be more powerful than bushing engines, but you will eventually have to replace bearings.

To say that any engine is better than another depends highly on the application. Pylon racing engines are different from 3D engines are different from Pattern engines are different from Trainer engines.

Find the application, then look for the engine.

Brad