The combination of several tracks recorded just below clipped....you'd have to turn every track way down to stop the master bus clipping. It's a waste of time. It's usually advisable to go in with an average of about -18dbFS (not a peak, an average, although peaking at -18 won't ruin anything). That may seem quiet, but when all the tracks are combined, your master bus is going to be peaking well above that. Digital recording gives you the opportunity for a considerable amount of headroom. A lot of it has to do with the fact that in digital the noise floor is lower than analogue, due to lack of tape whirring, and other things.
With analogue, it's a little different. You can record just below clipping, or even push it over, because whereas some amount of analogue clipping may actually add some character and warmth to the sound, digital clipping just sounds nasty. 0bdVU (analogue), equates to roughly -18dbFS (digital). this isn't exact though, it depends on your converters.
You don't want your master bus to be peaking just below clipping either. This is going to leave you no headroom for mastering for a start. If I recall, I don't generally let my master bus go above -6dbFS. The master fader itself, I always keep at zero. If you're having to turn the master fader down a lot, your tracks are probably too loud. If you have to turn all your track faders down a lot, again, your tracks are probably too loud.
Going just below clipping....on it's own, is not going to make anything sound better. the actual sound will be exactly the same. It's just needlessly louder.
I've probably made a couple of minor mistakes in what I've said here, because I find it easier to undertstand it than to actually put it into words. So I trust someone will correct those, but this is pretty much the basics of it.