True, you and I don't share how we hear the SM3 and UM3X, which are two IEMs that seem to have a love/hate relationship on here. You also didn't hear much difference between your ES3X and your UM3X from what I remember whereas I hear what I term moderate to large differences between the only universal I still have, the SM3, and my customs.
I do agree that getting other opinions is a smart move, but equally as important, if not more important is to try to figure out who hears things the same way you do and then the experience of that person will be much more relevant. For example, |joker| and I pretty much hear things similarly, at least with what we have both heard, but there are differences. I would trust his reviews for my hearing to the extent of where I know we differ (amount of bass). But, we don't differ consistently so I think our hearing differences are more than likely due in large part to fit, tips, and insertion depth of universal IEMs. Which brings me to my next thought...will the differences from person to person for customs be as large as it is for universals? Customs should, at least for a much higher percentage of people, take out the fit/insertion depth issues of universals.
@ Poetic: First, thank you very much for the compliment. I believe that sound signature plays a part in perceived space as well as being open backed among other things. I have heard many warmer IEMs that have sounded spacious and when the mid-bass is EQed down the soundstage shrinks a bit. From my logic of A > B and B > C therefore A > C, I would say the IE8 has a smaller presentation than any of my custom IEMs. Of course, I can't verify that unless someone wants to send me an IE8 for comparison, but the EP-10 Plus is a step above the other customs and it is both warm and open. My other open custom, the TS842 has a soundstage size that is about the same as the Kozee X3, which uses vented BAs. And project86, a reviewer I respect and trust, said the Merlin did not have a larger soundstage than the Miracle, if memory serves. So, does venting a BA into the hollow shell affect the overall space? Not to mention the particular track as I have experienced situations where for one track, one custom will sound larger, but for another track things are flip flopped. While I can rank my customs in terms of size of the soundstage, the source and track could cause the results to change.