MS Edge is a fast, lean, and efficient browser. When I play around with underpowered WinTabs, Edge consistently has smoother browsing (load times, scrolling, etc.) all around, when compared to Chrome and FF. It simply uses less RAM and CPU compared to the competition. Therefore, it's not surprising that it fares better with battery life comparisons. If they made even more improvements lately compared to the last time I played with Edge, I congratulate them for a job well done. Edge is indeed much more efficient than their competition, and as a web/software developer, that makes me appreciate their efforts on that front.
HOWEVER, that does not excuse their crappy security model. Anyone that's watched recent hacking events should know that Edge is the laughing stock of the bunch when it comes to vulnerabilities. Some of it comes with being the younger browser of the bunch. But that shouldn't really be an excuse in this day and age. I can't trust a browser that is so full of holes.
I'd appreciate if MS focused more on closing gaping security holes than a few more % on arbitrary benchmarks that become meaningless because the target audience is too afraid to use the product anymore.