You have to realise that if you do 10x10min or 5x20min you'll capture the same amount of photons and when you stack the result might not be that different but for the camera read noise. That's what I have observed doing testing anyway. Nowadays I don't bother going past the 20min mark if I'm impatient that is
Shooting more subs gives you the flexibility of having more data to choose from. The hyperstar is great for that because I collect so many subs. I can dump half of them and be choosey. Not the same when you have your 5x20min hard earned subs.