In bodybuilding a lot of people like to compare one exercise against another. Lunges versus leg curls, triceps kickbacks versus extensions, etc. One of the most common comparisons I have come across is that of hack squats versus regular squats, and people wanting to know which is the best.
My answer is always the same: There is no best!
They are both very useful to you in slightly different ways, and will certainly be useful to you at different times. I’ll explain to you how and why.
Hack squats, for instance, work the vastus medialis (lower, inside area) of the quads more than regular squats. If performed with a barbell in the old school style, hack squats also help to improve grip strength because you are forced to grip the bar firmly to lift it just like the dead lift, which you are not forced to do in regular squats.
Hack squats are also very useful to people who do not have a power rack or squat rack in order to safely perform regular squats.
Of course, both squats, overall, work the legs extremely well. But, let us not forget that variety in bodybuilding is the key to continued growth. Not only does it give the mind something new and interesting to comprehend, thus preventing boredom, but it also prevents the central nervous system from recognizing too-familiar (stale) movements and allows for continued growth.
Therefore, alternating between hack squats and regular squats is a great way to stave off staleness in your training routine, just as alternating is a great way to reap the particular benefits each squat variation has to offer.