So basically everything you do you could do with a rMBP + iPad. This nullifies pretty much everything else you said.

Again, if we talk about only owning one device, I can see how the surface (not the book, with its 2h battery life without the base and general bugginess) might have a case. It's about trade-offs,

I don't understand why you were mentioning pixel density. at that ppi, they don't matter as much, and the screens on new Macs are far and away better across the board. They also don't seem to have better battery life to the point where it might be relevant. I'm aware of MS BS estimates. It depends a lot of what you do.

I think everything else you said is also FUD. Surface devices have all at the best the same CPU line-up (now updated) as the Macbook Air. You lose CPU power and sustained performance Vs the 13" rMBP, you have less than half the CPU performance of the 15" model.

The ESC key... The DRAMA! Just put it there in the touch bar, or re-map it to the capslock button. Solved.

A Lenovo laptop comes with poor quality spyware and lots of vulnerabilities, so it is never a option. Also, good luck with those 18h.