As I remember it.. my custom fit UERM sounds flatter (more neutral) than the tour demo that James sent around. My custom fit UERM is less peaky through the upper mids/lower treble and possesses less midbass emphasis than the tour demo. There has been some speculation (and perhaps even confirmation?) that old UERMs sounded slightly different from newer UERMs.. but by old, I think we're talking about some of the earliest UERMs.. those made around the release of product. I think UERMs over at least the past year or two have a uniform, consistent sound. Again, this is all speculation on my part based on what I've picked up in conversations.
I wrote some stuff to Idsync in regards to the Tenore vs UERM.. might be useful here:
Warning: Spoiler! (Click to show)
Comparatively, the Tenore will sound warmer, more laid back, spacious, smooth, and organic. The UERM will sound more forward, intimate, crisp, bright, and analytical. The Tenore almost feels like a UERM that's been tuned 'for the masses.' More specifically, the masses -with very discerning ears-.. and those not requiring the pro monitor sensibilities the UERM was designed for. Therefore, I find the UERM and Tenore more complimentary than adversarial.
I find both the Tenore and UERM wonderfully detailed.. the UERM is sharper, more crystalline, and deliberate about resolution.. while the Tenore is more laid back and unassuming. BTW.. I popped the Tenores in and listened to a couple of live Sade albums while going to bed last night.. totally awesome.. I was enthralled with how the audience noise (cheers, screams, etc.) imaged on the Tenore.. much better than many $400-$700 phones I've heard.. really really cool.