Нашел только сообщение на форуме от пользователей, но если порыться где то было и от авторитетов утверждение...
http://forums.klipsch.com/forums/t/103823.aspx
The Custom 3 are the best sounding. They have 2 armatures (drivers) and a crossover in a reasonable sized package.

The IMAGE have one very high performance very tiny armature. Check out the Klipsch headphone pages for pictures to get an idea.

The Custom 3 is closer in size to ear buds but instead of cheap ear buds (ouch, those things hurt) the Custom 3 are extremely high quality in ear monitors that are quite comfortable. They may work better for some applications as the bendable wire can be used to hold them in place. It does take quite a bit of effort to get the Custom models inserted and oriented correctly to obain a proper seal required for optimum bass response (I own a set of the Custom 2 and it took a while to get them oriented correctly).

The IMAGE on the other hand are very small by comparison but probably a little lower in absolute sound quality but are exceptionally comfortable and very easy to use - just stick 'em in and are very unobtrusive as they pretty much fit in the ear canal. Just pop them in and you're good to go. I tried these as prototypes last summer and they are incredible. The Legendary Sound of Klipsch that fits in your ears. The IMAGE also have a way uber coolness to them. The incredibly small size is why they're more expensive.

In any case, the sound quality of either the Custom 3 or IMAGE is AWESOME. You can practically feel the bass in your head. Crisp highs, thundering lows. Can't go wrong with either one. There's a lot of good informative posts in the Headphones section.

The short answer

absolute best sound - Custom 3

absolute comfort and ease of use - IMAGE

One can't go wrong with either one IMHO. Personally, I'd opt for the IMAGE as I mostly use headphones working at my desk and they're so much easier to use and the ultimate in comfort. During my demo time they were barely noticeable, forgettably so, except for the wonderful sound.

The Custom 1 should crush your iPhone ear buds. The Custom 2 are even better - 2 armatures but no crossover - more thunderous bass and a little clearer highs and less distortion than the Custom 1. The IMAGE are next up in sound quality smoother and more extended than the Custom 2 in an insanely tiny package. The Custom 3 with 2 armatures, one optimized for bass, the other for treble, with a cross over are even smoother and more extended.