IMO no variations are as good as the good old "SQUAT". It builds your overall leg size. I noticed years ago when I started squating that all my lifts went up.

I would suggest front squats to a person who's lacking in quad development and or if that person was splitting his hams and quads up and training them on different days.

If you are training your total leg in one workout I would suggest doing squats, hack squats, Stiff leg Deadlift, leg curl and leg ext. the latter two ex. being optional.

PS dont forget to train the cows!!!!!