Welcome to FlyerTalk!

"Best" is a very subjective term. What is "best" to you may be far less than "best" to someone else. For example, on your topic, just flew a 787-9 SFO-AMS in 3A, and I am 6'1". The footwell size was fine and didn't think for a second about it. But Mrs BlueZebra, who was in 4A, was not happy with the window alignment. To each, their own. By the way, 1A might be blocked for crew rest.

Note what the previous poster linked to. There are threads like that for every airplane model UA flies. Looking around a little will get you tons of info.