I have not heard the Shure SE535 because the new recommended red edition goes for ~$550 on Amazon Prime, but I can say the Westone 4's (no R - costing $300 on Amazon Prime...$250 cheaper than the Shure) is no doubt the best I have heard. For costing nearly 2 times less, I think Shure has some rough competition.
To sum up my research, people seem to like the sound stage of Westone 4's better.
Westone - open/realistic/balanced (there is a lack of noise about these because people are really happy and don't go online to complain...they are near perfect...not much to say)
Shure - thick/up-close/unbalanced (mid-heavy and lacking highs... some people would call this "muffled," but others call it 'warm,' ‘dark,’ or 'intimate')
IMO, after trying 10 different IEM's ranging $150-300 (excluding the Shure SE535 LE Red - really hard for me to justify $550... I think they're way over-charging), I can honestly recommend Westone 4's as leader in the pack as far as IEM go. IMO, listen to the forum poll, which currently favors the Westone 4's by a good margin. I may try the Shure's, but so far I don't see why because there isn't much to improve on the Westone 4's.
I do think it is really hard to gauge which earphone sounds better...it’s all opinion after all...people's ears are different and we are just stating opinions without data to back it up. The technical specs don't really dictate sound quality, though on paper, Westone 4's (4 drivers) look better than Shure SE535 (3 drivers.. 1 of which is combo).
Side note: I have compared the Westone 4's (best of the best) to the new Bose QC20's and honestly though the Bose are worse sound-wise, they still sound decent (good enough to not be called 'bad'). The Bose have a thicker bass (not as tight as Westone), but the mids and highs are 'low key'...probably intentionally tuned for comfort; overall, I think the listening experience is really good, but using the Westone 4's for the first time, I immediately heard everything "open up" as if the Bose have a fog, even after they opened up from break in. Regardless, once you get used to the Bose, the sound becomes comfortable and you don't care...add in that they have noise canceling that is a lot better than the passive isolation of other earphones, I would recommend these for everyday listening in noisy environments (almost everywhere...), where you want background music rather than sound perfection. The Westones are better as monitors for "sit down and serious listening" to...for which occasions I would honestly rather listen to my $5k home theater setup.