Golf II GTI 16V or BMW 325i as a slalom car?

Hello guys, I’m planning to build a slalom car and I don’t know if I should get a Golf II GTI 16V or a BMW 325i now. so I’d like some infos about the size of the golf and the bmws. can you please tell me and vll give me some tips, which car vll is the better one? many thanks already for the infos mfg