If you want an in depth answer then ask this in the Glow Engines forum.

Basically:

ABC = Aluminium, Brass, Chromium. This means that an Ali piston runs in a brass sleve, which has been Cromed.

Ringed = there is a small ring (sometimes two) at the top of the piston to ensure that there is a tight seal between piston and sleve. (note many ringed engines are also ABC or ABN

Non Ringed = engine relies on the accurate machining of the piston and sleve to get the tight seal (usually by a pinch method near top dead centre)

ABN - Nickle chroming rather than chrome

BB - Ball Bearing (ie proper Ball race rather than a plain bearing)

As for which is better, only certainty is BB is better than plain. Rest depends on the engine.