My guess is that you will see the standard "discussion" between the Sony 888 and the Sennheiser MX500. Both have their strengths and weaknesses relative to each other and overall, so personal preferences usually dictate one's choice.* Do a search to find the many threads that have discussed these two.
I personally find that both are too large in their driver housings and air-shaft to be comfortable in my ears for a long period of time. If I really need ultra portability with earbuds, I use a pair of cheap (~$5-8) Sony 821's with smaller 13.5mm drivers. Yeah, I pay the price with their lack of bass, but after listening to them for a few minutes my ears adjust to the sound and they are so small I can pretty much forget I am wearing them.
However, when I can (usually) wear something a bit bigger, the Koss SportaPros are my choice for best portable headphone. They share the same drivers as the KSC35's, which I have never heard personally. Most all KSC35 owners that have heard both contend that they sound even better than the SportaPros. I personally like the dual-position headband of the SportaPros, and they are ultra-comfortable.
* There are others, like the Sony 484 and an older Aiwa, which I have never listened to since they are long discontinued and not available new, but those who have say are even better than today's current offerings.
