Re: Charge for trainee and Journeyman
My company bills significantly less for apprentices.
We also tend to run small jobs, and troubleshooting as T&M, while larger installs go in as flat bids, with a reduced rate on labor if it's over say, 100 hours.
As far as what's "best", well it's some of this and some of that. You can't lose money on T&M, but then, you aren't going to make your vacation money on it either.