Actions Speak
The actions of Mozilla and Slurp speak volumes about the organizations. One acknowledges reports and deals with as fast as possible. The other seems to be either too disorganized or suffering from bureaucratic infighting to react. Firefox will get patched in a reasonable time period without prompting; Edge might get patched when some slob bestirs himself to actually do something possibly after several months of harassing.
It is obvious which browser should be trusted: Firefox.