XL = Plastic everything
SA = Aluminum body, plastic head and rotor
S CF = Carbon fiber body, plastic head and rotor
SE = Carbon Fiber body, metal head and rotor
SE V2 = Basically a SE with all the complaints fixed

Those are pretty much listed in order of price and performance.
Each kit can come with a slightly different motor/esc, the 450L (3550kv), 450XL (3700kv) and for esc the 35G and 35X (not sure what the diff for esc)