I have the Shure E3C's and the Etymotics ER-6's.
I haven't tried the Westones or UE's, but I find the Etymotics with the foam tips to have a good combination of comfort and isolation -- they don't insert as deeply into the ears as they do with flanges, and they're smaller than the UE's, so there's less "Shrek Effect" ... still somewhat low profile, as they're so small and light.
I first had the Ety's and used the two-flanged tips they came with, and was very impressed with the isolation ... but the fit/seal/sound changed slightly with yawns and moving my head up and down on plane flights (and they were somewhat tricky to get out of my ears, due to deep insertion).
I then got Shures and used stock foamies all along, really liking the "low tech" effect of using the foam tips. There is still isolation -- just not as impressive as the Ety's with the flanged tips. On a five-hour plane flight a few days ago, I enjoyed good isolation with the Shures in the (noisier) back of the plane. Whether playing music or just leaving them in my ears with no music playing, the ambient roar of the airplane cabin was reduced significantly, making for a less fatiguing flight. No discomfort, aural or physical.
I've switched to stock foamies for the Etymotics, but have not used them on a plane yet (which I consider the real test). The dark Etymotic foamies seem to be a little larger than the yellow shure foamies, and depending on one's ears, might create slighly better isolation. Even if they were less isolating than the Shures with foamies (and I think they're a little more isolating), they would be very comfortable for me -- and easier to put in and take out -- with the foam tips.