Well not to many of these headphones should be considered portable in the least. The only other noteable headphone I can think of would be the Sony MDR 7509 Pro's which are about as nautual of a sound( Balanced, absolutely incredible sound sig for recording or tracking.) They aren't small but they isolate fairly well, got to use them last week and though it's not my personal favorite sound sig( I'm a V shaped person) I still found them to be very good for what they are.
None of these headphones are small, the Denon's hardly isolate and almost sound open, the Ultrasones( all of them) are more forward and punchy OR weighty in the low end. The Shures are uncomfortable for some. The M50's are decent at most things, they don't do much wrong especially when you consider their price.