Gain Staging (i.e. +6 db = 0?)

[carmichael]

Sorry to post a question that seems so elementary but I think I'm losing it.

I've always been careful to set my audio channels so they do not peak above zero anywhere in the channel (including internal clipping within the plug-ins) and to set the channel levels so that the bus never peaked above zero even without having to attenuate the bus with a master fader. My friend claims that with 6 or 12 db of headroom, it is better to peak above zero and approach the true zero which is +6 or +12 db (depending on your protools setting). Even when he bounces to disc, he doesn't bother reducing the master fader to peak below zero.

I feel that my approach is much more sophisticated, yet, I can't hear any clipping in his mixes and they almost sound better (richer) at those high gains than they do after I've bothered to "fix" his gain staging.

What do you all target for:
1. Peak level on your master bus (ie for bouncing)?
2. Peak level on aux channels?
3. Peak level inside an audio track (ie at the input of the plug-ins)? I have horrible noises using wave q10 eq even without any red clip alerts when there is an eq gain and the overall level is attenuated on the output fader.
4. Is is better to keep channel output low or to use a master fader on your buses.

Thanks!