I want to like Edge, I do, I use it frequently trying to force myself. However, on the Insider Rings it is more trouble than it is worth a lot from what I have experienced. Random crashes, the funny context menu bug that continues (albeit not as bad as it was at first.) It does run smoother than Firefox in most cases, and considering that after the third crash or so I am generally fed up with it and shutoff the Surface Pro and do something else, so yeah it saves battery life.
Seriously though, it is faster and does save battery life compared to Firefox. Firefox is very clunky feeling even without extensions enabled. If Edge would fix bookmarks issues and start carrying over the extension settings from system to system (Ublock for example how Firefox handles it) I would probably go with it full time on my not insider build system.