F or M depends on how close you like to be. I've sat in both, and I found F was just a little too close for my liking - overwhelming sometimes, and I wasn't getting the full effect of some of the staging. However the detail was unparalleled, we could see ever detail of the actors expressions. I told my partner after that I really liked the seats but I would not want to sit even one row closer.
Also sat in M, and really enjoyed it. A good seat, without the intimacy of the closer ones but a great overall picture. I understand the seat I sat in (M12) is now considered a premium seat... I would not consider it so. It was not the same experience as sitting in those prime orchestra seats. Well worth it at the 250 I paid, but not the 750+ they charge now.
Overall if they cost the same I would prefer F, but if you're spending the big $$$ I would see if there was possibly something one or two rows back. Row J was my favourite, just the perfect spot to take everything in yet feel close to the action.
Have not yet sat in mezz but I am hoping to soon. Supposed to be a fantastic view of the choreo/staging