Well...anything to share with us on your investigation?
Yes.
First, let me HIGHLY recommend Steve at SRS Tactical. Sight sponsor that I hadn't clicked through to until this inquiry. I'd never met him before today. He's a very knowledgeable and very patient fellow who was very generous with his time in helping me figure out what will work best for my needs. Best prices I've seen for that kind of high-end product, too.
Next, I was looking specifically for muffs for RO use, with noise reduction being the most important factor, not worried at all about being able to cheek a buttstock. One active pair for outdoor range use, and one passive pair for indoor use around braked carbines (max NRR).
I wound up choosing Peltor TacticalPro muffs (active) with the additional gel earcups recommended by Unregistered_ above, and Peltor 105 (passive).
Since NRR was my most important factor, the MSA product was not a real option for me. I can seen why people would consider them for use while shooting, since both Peltor muffs that I chose are bulky (incidentally, neither prevent me from cheeking my shotgun or carbine, but this depends on your cheekweld and your stock). The TacticalPro have NRR 26, and the 105 are 30. They were the highest noise reduction ratings available in their respective classes, so once I was assured that the fit and construction was acceptable, the choice was very easy.
Fit around eyepro (as mentioned above) and hats is critical to the muffs working as well as possible, so the addition of the gel earcups made a lot of sense to me from the first time I heard them recommended. Not to mention that they are more comfortable. But from a perfectly noise reduction standpoint, I'm very happy with what I walked out with.