I've only been in one -12, twice, and didn't find the noise objectionable. I do know that my previous generation Bose, which worked so well in Cessnas, didn't seem to work well with the Rotax in my CT. Lockwood did a sampling of various headsets a couple of years ago, and concluded that, at the time, the Telex Stratus 50D did the best job in the Flight Design CT. I bought 2 sets and haven't regretted it yet. Since then there are other products that are probably better yet.
I don't think it's that the Rotax is noisier than others, just that the frequencies are different. Like Tony, I damaged my ears over time doing many of the activities he mentions. In those days nobody used hearing protection and not much was available anyway. Those of us who tried various devices were laughed at. Now we pay the price.
So, sample the various headsets, read the reports, and buy the best available for hearing protection with comfort being secondary. Most modern headsets are reasonably comfortable anyway and these days my butt wears out long before I get bothered by a headset. Once the ears age gone, they're gone and hearing aids don't correct the problem like glasses correct vision problems.