I would like flows with a lot of strength based elements. Not really having to be inversions or tricky poses, just things that really make me feel my muscles working.  I don't love lifting weights and I have found that given the right class I can get similar benefits from yoga.  I'm not really looking for gentle, but strength combined with a stretch to ease off after the hard work is great. I do like it when you give cues for how to make movements physically accessible or to increase the benefit or work. The classes 45 mins and under also work great in my schedule.