Honestly, it's all personal preference, comfort, and experience. There's no "starter bike" that applies to everyone. Some people might find a 750 too powerful to start, but you also get others saying it's enough power for them and they can grow into the bike. You never really know until you try it.
I would suggest going to a dealership and sitting on the bike. Just make sure you're don't have anything on you that may scratch the paint (i.e., belt buckles, keys, etc.). If you're lucky they might even allow you to take the bike around the parking lot.