As Miles is an NCO and Geordi attended the academy, I would have to say that Geordi has more scholastic training, however, it can be argued that as O'Brian served as an NCO far longer, he has more practical experience. This is a tough question to answer
^^ Miles O'Brien was also an officer (first an Ensign, then a Lieutenant) on the Enterprise, so he too attended Starfleet Academy.
He got busted to CPO for some unspecified offense, because he was a Lieutenant, j.g and then a Lieutenant early in ST:TNG. He is depicted as a major transporter expert on the Enterprise-D, and transporter technology has to be among the most intricate and complicated known to Federation science. There was probably some cognitive bias about O'Brien being a lesser technician than Geordi, since he was not "inner circle", as Geordi was. O'Brien certainly is a formidable expert by the time of ST:DS9, even becoming an expert in Cardassian technology mid-career. As an engineer, O'Brien is no slouch at all ProfessorTrek 18:43, August 17, 2011 (UTC)