Poll
50%
33%
17%
O'brien is my favourite character, so I may be a bit biased, but he did manage to keep Deep Space Nine (a cardassian station) up and running without being fully equipped to deal with it. I've not seen enough Enterprise to make an informed desicion about Trip, and B'Lanna was interesting, but as an engeneer I don't think she's up to O'brien standards.
EDIT: Sorry about all the spelling mistakes there, but I just got up