RE: Squats vs Leg Press
With years of a dodgey back plagueing my squats (and DLs) I have relied heavily on the leg press in the past. Glute developement from them has been OTT, quad developement, despite being fairly strong on them (over .5 tonne in some cases) has not been so rewarding.
Squatting however, particularly front squatting, has produced very satisfying gains whenever I have been able to incorporate them (which has been fairly regularly the last couple of years). I would assume this is a combination of muscular (fibre) recruitment, GH and IGF-1 stiulation.....
The fact that they (squats) are, as you say, the best over all mass developer, does immediately imply that that overall mass will also be proportioned to the quads anyway, so you have in part answered your own Q.