It all depends on what he meant with MP3 player. I mean, I can understand that, if he believes that Apple iPods are the only ones with an Hard Disc (which is untrue), that he believes that iPods are better as you can store more songs. I mean, on a normal mp3-Player (so without harddisc, that is), you can not store 20 - 30 GB, as they are not out yet.
So conclusion: His statements are rather true, if he compares only the iPod and mp3-Players without Hard Disc. And then, he is right: -More storage place. -Rechargeable battery.
He forgets however, that there are loads, yeah loads of other Music Players with Hard Discs.. Sony, iRiver, Creative, and many many more. Compared to other HD-players, the apple iPods are... dare i say it.. not much.