Oh, I love 'em both and find that I reach for these more than most of my other circuits. HSTA works my legs like no other circuit. All of the leg exercises are tough - especially because they follow a set of leg presses. But Sit and Stands and hover squats are the two I dread more than any of the leg presses. I'd say between the two, I do this one more.
HSC is fun and very varied. I really enjoy it, too. I guess it depends on what you want. I like to focus more on lower body, so I love the demands of HSTA, but if you just want a fun circuit, HSC is a blast.