Blanket statement.
The ROM prioritized depends on what's required by the individual.
Sub-parallel is ham/glute-dominant...and it also places less overall load on the quad.
"Less overall load" as compared to squatting to 85-89 degree knee flexion.
I've switched from parallel to ass-to-ground...and guess what?
Overall thigh mass decreased.
Teardrop size increased marginally...glutes/hams got thicker.
But for an already posterior-chained-dominated bodybuilder, this did my physique zero benefit.
In conclusion... there is no 'best' manner in which to train ANY bodypart
'best' for a noob would be cyclic inclusion of all ROMs.
Or..better yet, varying ROMs from work-out to workout.
An intermediate would be 'best' served by including both partial and full ROMs within the same workout.
For myself, I've gotten to the point where instead of using multiple movements.. I use the same exercise but with modifications.
e.g.
I leg press to warm-up my thighs; glutes; hams; knees and hip.
Then i squat to parallel heavily to overload the muscle complex.
upon completion of my target sets, I squat ass-to-ground to isolate/stimulate the teardrop region.
A sidenote: Modifying an exercise proven to work makes more sense than varying exercises.
Variety is the curse of the bored.
-CNS