While I'm not too keen on synthetics, they have come a looong way. My only question is how important is it that you can drop it in the washing machine, take it out of the dryer and put it right on? 100% cotton or linen can be a bear to iron out smooth, and that takes time. A blend of say 35/65 poly/cotton can come out of the dryer and go right on your back. Yes, it will look sharper if ironed, but that is mostly just touch up. Again, the choice is up to you. I would, however, avoid 100% polyester, as that can get a slimy feel on a hot day very quickly.