If comfort is a concern, the w4r has very few if any real complaints/reviews about being uncomfortable. The 535 on the other hand has a reasonable amount of complaints/reviews about them being a bit large and/or uncomfortable.
To elaborate on that a bit. The 535 is a tiny bit larger and less smoothly rounded on the back edge. This causes it to contact some ears and feel like it's poking. They are also simply a bit (very small amount) larger and a decent amount heavier than the 4r. The cable is also heavier. All these things contribute to the possibility of you finding them more uncomfortable. Some people have no issues at all. However, the 4r is extremely light, more smooth on the back of the housing, has a lighter cable and doesn't really contact the edge of the ear or weight it down. So for comfort, there is a much higher chance you'll find the r4 comfortable. I'd say out of the box the 535 sounds more engaging while the 4r sounds a bit more balanced overall. But both aren't perfect. With EQ they both sound better.
If you have large ears, the size may not matter, but the weight might still. If you're worried about comfort, get the 4r. If you're worried about anything else, get the 4r. ;) haha But really, they're both great. I think most people go with the 4r because they don't lack as much treble.
Thank you very much for your help , I think I'll go for the 4R then.
One last thing, what do people mean by saying they find the 4R boring?