Bought the PRO 30 today. Spent most of the day with them. Here are my thoughts and impressions:
1. Design and build. Improved, without a doubt. The housing is smaller, definitely sturdier. Feels more damage-proof than the UM3X (whose housing fell apart numerous times, with glue drying out). The cable is OK. I can really appreciate the rubberised cable braiding bit that goes behind the ear. Not a big fan of the connectors. Ergonomically, the PRO 30 is clearly superior to UM3X (for me), of course having in mind that physiology of the ear canal differs for everyone. Due to smaller housing, they sit comfortably in the pinna. Which results in better isolation than with UM3X, due to them not moving and sitting flush. Tested with an hour worth of playing drums. Overall, I'm pleased with the improvements.
2. Sound. Can't notice any difference. Upon first listen, I thought I noticed that they are a bit rougher and wobbly on higher volumes, while also being a bit harder to drive. But I thought that was due to not using any headphones for a couple of days, with ears taking a break of sorts. That seems to be the case. I can't hear anything that would suggest they tampered with sound signature, balance, soundstage, tone and all that stuff. Maybe I'm not trying though, which again (in my opinion) proves the point that the sound is the same, and I don't have to try and find the differences, they are just not there.
3. Conclusion. For someone on the fence, the PRO 30 are the ones to get if you were planning on getting the UM3X. Even with the UM3X price going down, I would still pay the difference and pick the new edition over the old one. But most improvements come to light under specific circumstances, in my case while on the drums, and may not be as beneficial to others. But if you own UM3X, there's absolutely no reason to even consider purchasing this facelifted offering. I'm a bit puzzled by the fact that Westone went for iteration rather than improvement, but I guess they wanted to nip and tuck the workhorse and bring it more or less to today's standards. To conclude, I am a bit disappointed, although still quite satisfied, since I just love my UM3X, and wouldn't have bought the PRO30 if the right speaker didn't fail. And the PRO 30 is basically just that - prettier, slightly improved (design-wise) UM3X.