Have both side by side because I wanted to make sure I wanted the XS over the max and I'm returning the max tomorrow. I had a 7+ but the max feels even bigger due to the screen size. Very hard to use with one hand and the size/weight was noticeable in my pocket. The screen is awesome and its great at home while relaxing, but I run around too much during the day to give up easy one handed use. It's definitely harder to use than the plus due to the fact that your finger has to cover from the absolute bottom of the device all the way to the top edge (which is now used way more due to control center being top right). I could use my plus one handed, no chance with the max. Reachability is also much more difficult to activate compared to the plus. For two handed use the phone is great, but anyone that needs a phone thats remotely comfortable one handed I'd definitely recommend the XS. I'm also 6'1 and have large hands.
Additionally I didn't really feel like I benefited much from the larger screen as it doesn't really display much more due to the aspect ratio and the lack of iOS multitasking. The biggest benefit for me is the keyboard as the slight increase in width does make typing easier. I'd ideally prefer a shorter but wider phone compared to the current max.
Also no unique features to the max (I bought my 7+ for the dual camera) and the battery life gap seems smaller than ever. If they had a triple camera or something like that they could have possibly swayed me, but trying both side by side it's clear for someone that uses their phone while walking the dog and longboarding that the XS is the way to go, as its the same phone just more compact (no feature tradeoffs). The pocket bulge just wasn't a good look either. Not sure if it was the weight or maybe the fact that I'm just wearing better fitting pants (compared to when I had my 7+), but the max made my right thigh look like a brick.
Maybe future iOS updates will change my mind, but the tradeoffs for me were too great to choose the max and for me I prefer portability and ease of use for my phone. I have my laptop and iPad for the big screen stuff.
Sign me up day one for an OLED (or mLED) MBP or iPad though, these two displays are magnificent.