This was REALLY helpful. Thanks a lot!The K10 is great. I'm a fan too. imho, the K10 has a bigger soundstage, and is more "omni-directional" - in the sense that I had a better sense almost of where each instrument was being played, where the vocals were coming from etc. The highs were also better in my opinion. Could hear the natural decay of a crashing cymbal and ghost notes on a snare. Overall, however, I felt that the K10 came across as more balanced and subdued, but also more accurate.
My take is that the S6Rui is the punchier of the two, and more fun. Slightly smaller soundstage, but makes up for it in liveliness and just sounding like a damn good mix. Complex arrangements really stood out because of the musicality of the tuning.
I think I would go for the K10 for critical listening. The S6Rui, for the everyday jive. Just my 2 cents.
I must qualify that (a) i did not compare the two side by side, neither did I use the same songs; (b) my experience with the Fearless line is limited only to the S4 and S5T (which I did not like), and the S6Rui (which was amazing to me); (c) I also do not own the K10, just happened to spend about 30 mins listening to it; and (d) I am by no means a professional, just another geek.
Cheers!
Since my Laylas are pretty neutral I'd probably go for the Fearless. They are also MUCH cheaper. I might jump on the Massdrop drop.