I think it would still be interesting.
Win10 + Edge vs macOS + Safari.
In the end the user does not care which OS runs in the background, just which platform offers the best experience - in this case the longest battery time.
There are plenty of suitable comparisons from which one can make an educated guess. In general, Macs do better than comparable Windows machines in browsing endurance tests, and Safari clobbers every other browser it has been tested in for battery life (I have _not_ seen a comparison of Safari to this new version of Opera, but judging by its performance relative to Chrome it could be competitive with Safari).
Safari, of course, has lots of support for ad blocking short of Apple actually doing the ad blocking itself. I suspect Safari + ad blockers would be the best option across the board (it absolutely rocks on iOS devices).
It is, but with the Boot Camp drivers, it seems like a fair fight. Obviously both OSes do some things behind the scenes that impact battery life, but we hope both are tuned to conserve battery when not charging. Though to turn the argument around, given that ChromeOS isn't known for wasting a lot of battery while browsing with Chrome, having less OS is probably a boon.
