I'm out of the game now, but have used and specified laptops for corporate environments, from 13 - 16" and I would not want to try to work on anything smaller than a 14" screen. 15" and above tend to also have a full numeric keypad alongside the QWERTY, which is a godsend if you do a lot of number crunching.
I always seemed to end up with HP kit - Elitebooks - which I always found solid and reliable. It was generally a shoot-out between HP and Lenovo, and HP generally won. Having said that, my personal laptop is a 16" Lenovo Thinkpad (with aforementioned numeric keypad). It's nowhere near as light and portable as the newer Elitebooks though - even taking the larger size into account. However, HP stopped providing built-in RJ45 ports a while ago - you have to make do with a USB-C to Ethernet converter.