The synthetics stink too much for my tastes.
That used to be the case with the old polypro, but there are modern synthetics which don't stink, even after several days. I particularly like the Medalist Silvermax gear I bought a few years ago. Very good for next-to-skin wear, and no stink. I have some Sitka lightweight long johns too, which are also really good. Both use silver, and this really seems to work to prevent them stinking.
I personally much prefer this stuff to wool or silk.
