This is wierd...I'm carrying out just such a test tonight using my iPod Classic, iPhone and a slightly older pair of iGrados (with the SR60 drivers, not the SR60i ones which are on the market now). The AKGs are very good headphones with lots of detail and very strong bass. They are a conventional over-head-and-over-ear design with some nice flexibility and accessories - you can turn them Into a headset or make them into a full noise-cancelling pair. You can't do any of this with the iGrados and they are a 'neckband' design which isn't always comfortable. They're also very big so make you look like Star Wars character. The sound of the iGrados is excellent but on balance the AKGs pip them for atmosphere.
My only criticism of the AKGs is that complex tracks sometimes seem to overwhelm them and the bass seems to swamp everything. They are also at their best with no background noise in my opinion.
At this price I prefer the AKGs sound, build (bits have fallen off my iGrados after 3 years) and practicality. If you have more £££ consider Audio Technica which are also excellent - I loved mine but some b*****d nicked them