Jett and Enya are the only two manufacturers that utilize AAC cylinders that I personally know of. If money were no object, AAC is the way to go. Similar to a lapped iron piston in a steel liner, they will last virtually forever with the proper care and good fuel. AAC is an upgrade to a Jett, true ABC is the standard with those guys, though some models only come AAC.

The most common ringed engine I've seen are the Super Tigres. They are great engines for the price but take a long time to break in.