I'm copying a post I made over on the Weston W60 thread comparing the two IEMs. I hope that's OK.
I thought nothing could surpass my beloved Sennheiser IE800s, but then I tried the W60s.
I can't say which one I prefer, as they are just so different. It's like 2 beautiful women; who can choose? The one I'm listening to at the moment is the one I find myself preferring.
The IE800s are more cohesive. They have a better mid-range.
The W60s have a bigger sound-stage. They are more airy and a little more revealing of detail.
However, I can't get over the impression that the mid's are a little weak. Sometimes that just lets the highs and lows shine more; sometimes it feels a little unsatisfying.
Overall, the W60s have a quality that I keep thinking to myself of in terms of a Japanese word, enryo (I live in Japan). Enryo is kind of like "reserved" but has different qualities. If you really want the last piece of something, but leave it on the table for someone else to take if they want, that's enryo. The W60s are like that: they don't force themselves on you, they kind of hang back and don't demand your focus, but if you turn your attention to the sound after thinking about something else, all the detail and beauty is there waiting for you to notice it.
One reason for this difference is that, while the W60s have a little bit more detail, the sounds of the IE800 have a little more "sharpness" or "bite" to them. If you've done any photo editing, there is a control called "clarity" or "sharpness" or even sometimes "structure." The IE800's have this setting turned up a little higher, so each individual sound comes across as more well defined, even though there is actually not more detail there. The IE800 is like the image of a rose taken with a medium-format camera but with the clarity/sharpness turned up, while the W60s are like a large-format camera with the clarity/sharpness left at standard levels. If that makes any sense.
I'll stop rambling now. Those are just impressions from somebody who doesn't know enough to qualify as an audiophile, I just like my sounds.