I totally agree with you that WP8.1 is far more polished than W10m right now, but even though WP8.1 is more polished than W10m, and RS1 right now is buggy as heck, I'm going to keep my 635 on RS1. I rolled back to 8.1 once, and at first I liked how stuff just worked on it, but then I realized that I'm giving up on a lot of the enhancements that W10m brings: Edge displays webpages better, better MS Office apps, a Photo viewer that shows local and OneDrive photos simultaneously on one page, and it can play animated .GIFs, the ability to save offline maps onto the SD card, improved Action Center, one-handed mode, a better organized Settings screen, W10m-only apps, among many other improvements. So I went back to W10m.
But perhaps the biggest reason I decided to return my 635 to W10m is, even though W10m on the 635 sucks real bad right now, it's getting all the attention, new features, updates, and the problems will get fixed sooner or later. WP8.1, OTOH, while polished, is totally abandoned, and it'll lose Skype soon, which for me is kind of a big deal. I hate how buggy this phone is right now, but I'll take that over abandoned. Kinda crappy choices either way, but there it is.