If you look at some of the new vehicles coming out, especially with HKG, I see a lot of models moving back to the old style sunroof - smaller in size and not panoramic with the plastic exterior side covers, but rather the piece of glass that is surrounded by all steel panel (roof). The panoramic roof is undoubtedly likely more desirable to consumers cosmetically, they look nicer (in my opinion at least) and offer a larger opening. I'm starting to think panoramic sunroofs are inherently going to rattle more than the traditional style due to size, weight, a smaller roof structure (steel portions), and they may have even more parts than a traditional sunroof (the two exterior side rails for example).
I'm not alleviating manufacturers of any blame for rattling sunroofs, nor am I surmising exactly what the cause is since it seems there are different fixes for different people, but the trend I'm seeing towards a more traditional sunroof in new models instead of what I otherwise view as the more cosmetically pleasing panoramic sunroof is likely manufacturers inadvertently showing there is an issue with the design of panoramic sunroofs that they cannot yet figure out.