We did the exact same thing one year. I think the cut scapes were better, if I remember correctly. Whatever the outcome was, we concluded with "we'll always cut the scapes" - so I assume it was that the bulbs were better.

Seems to be reasonable: keep the energy in the bulb rather than in the scape/flower.

I think you only leave the scapes if you want to propagate the garlic - but that's a multi-year process and I've never dove into it. I just buy seed garlic each year.