Well seeing as his contract doesn't end until October, he's probably going to end up waiting until October anyways and worrying about a new phone now won't do much good when a whole bunch of new options are announced. I mean even now that the HTC 10 has been announced and although it looks...

well if I had to I would go s7(preferably s7 edge if you're willing to go bigger) or the HTC 10 depending on how it actually performs.

Shouldn't you wait until October to think about this? A bunch of phones could be announced between now and then, most likely including the new nexus phones.

I have the M50x and find it quite portable (or at least portable enough for me to use it on the train during my commute everyday.)   As long as you have a bag to keep it in when you aren't using it the rest of the day it should be fine and I can't really imagine them being any less portable...