Read comparisons and pro/con's ad infinitum at www.head-fi.org on this subject. I have Senn 650, AKG 701, various Beyerdynamic, and both Etymotic and Shure SE530. The earbuds can be used successfully even without a headphone amp (ie into an iPod) but the big phones must have a headphone amp to hear their potential. You must also make sure, probably by experimentation, to use the proper sized earpiece with either pair of earbuds. The Shures and Etys really seal out external sound and are great on airplanes or at the gym, when you don't want to hear anything but your music. Outside sound leaks in with the bigger, over the ear phones. I don't think the earbuds are necessarily inherently or always better in terms of sound, but they _can_ be better because of the better isolation you get from sealing up your ear canal completely.
Hi end ear buds
I would like to hear experience from users of high-end ear buds like Shure SE530PTH which goes for something like US$ 450 to 500. Granted they do not require a headphone amp, but for the price one can get a decent pair of reputable cans from Sennheiser, AKG, etc., which I thought would have more uniform frequency response than these small sized diaphragms. Or am I missing something wonderful with these little buds ?