Hi Eric,
Great to have you back again! That school can be quite a timesink (and is why I encourage all my friends against going! )
Ooooh snap, that’s a shame! We need to get you back in action!
Josh and TJ would be able to talk most about it, as both of them rock Fibersen skinned shamisen.
I can say that Fibersen is the closest thing to natural skin, lightyears beyond regular plastic skin. Sawari comes through clearly and the san no ito is very sharp. That said, it’s not 100% identical to natural skin. I would say the difference of natural skin and Fibersen shamisen is general, you can tell natural skin is fresh and Fibersen is synthetic. But unlike regular plastic skin, both natural and Fibersen sound pleasing, just the difference from the materials.
One thing to know is that the sound quality of natural skin deadens after a year. Thus, no matter what quality the skin is, it will always sound more awesome when freshly skinned (new average quality skin will sound better than a 1+ year old high quality skin).
Comparing a fresh natural skin with Fibersen, natural will sound better. However, if comparing Fibersen with a 1+ year old skin, the difference is much more negligible. So, in planning for the future, unless you plan on reskinning your shamisen yearly (which none of us are ), Fibersen would make good sense.
Btw, it was great to meet your sensei Toshi san for the first time!