The suffixes: LA, FX, RX, AX, VZ, SX, etc. are just model designations (I think). Though "LA" is frequently referred to as "Lame" in the circles I fly in. ;-)

Some other designations

BB - Ball Bearing
ABC - Aluminum case, Brass sleeve that is Chrome plated. ABN would be nickel plated sleeve.
CL or C/L - Control Line (no throttle).
Ringed - piston has a ring (easier to break in)
II - Mk II - second model in a specific version