An ear-dangling contest... I like it
My point actually is that when you do listen in a less controlled way, then personal preferences and other unrelated things come in to mess up the mix, however independent you think you are (and I've always thought I was very independent). I set up this test a while back to just test out this hypothesis, and I've run the said test with sources which I've heard major differences before when I've run an uncontrolled test. I have done the same since then, mixing uncontrolled with controlled. The level of difference I've heard sometimes in the uncontrolled test which turned out not to be there in the controlled test are interesting. On the other hand if there is actally a difference in this type of listening then it's all the more worth noting.
I'm using the MDR-SA5000 today to compare the two after just the volume matching, without an audio switch. The SA5000 is relatively speaking something of a fart cannon and combined with their electrical characteristics make the bass fall-off of the iPod a practical non-issue... although the X5, having a flatter response even with these advantages granted the iPod still generates more low bass, but not enough to colour comparisons too much.
What really concerns me about the Photo in comparison to the X5 is that the notes seem to stand out less from the background, if I can put it like that. And yet the iPod does not suffer from hiss, at least not to any extent over the X5. Basically, the sound of the X5 has slightly more presence in the presented soundstage. The problem is not in the lows... it's across the whole frequency range and certainly easily heard in the mids.
I could not say this sounds in any way "bad", but this is not what I was hearing with previous iPods. Before, I could actually say without any reservation "this is better" when I ran the X5 comparison. Now I can't.