I'd say the Westone 4 is more detailed and has more accurate imaging, but the Se535 has more exciting imaging with more sparkle, stronger mids (perhaps a tad too strong) and more bass impact. W4 however has better instrumental separation, a much wider sound stage and more balanced sound across the board. Only negative for me is the bass, even EQ'd it's still not punchy enough, though it does have excellent control and texture.
I was using both earphones straight out of the iPhone 4. My JDS cMoyBB 2.03 should arrive in a few days and then my RSA SR-71A a few days after that. So I'll report back with findings once they arrive.
Here are the final EQ settings I used for each IEM straight out of the iPhone 4 using EQu at 'loud' preset.
That's playing it safe and balanced. But personally, what with having a slight affection towards bass, I go for this with my W4's.
For the SE535's.
Thanks Naim, have you try the Fiio E1 portable amp with your W4? When I had my W4 that little amp added a bit of bass impact and sparkles to the presentation. What I like about it is the fact it is tiny and has a remote control line function built in. It's great when you don't feel like lugging a big amp around, they're only $22 USD and available at Fulcrum Audio