I prefer Unbound Merino to Smartwool for shirts, though Smartwool's socks are better than Unbound.
How itchy do those get?
Less ichy than cotton
It's usually a fine wool that is very nice on the skin, not the itchy wool you may associate with a chunkier sweater.
How do Darn Toughs compare? I've managed to wear through 8 pairs of costco wool socks without loosing any, so the idea of a lifetime warranty sounds promising.
Darntough socks last much longer than smartwool for me.
I cover thousands of miles a year on my feet. Darn Tough socks live up to the name. I've never put a single hole in them. I've torn up socks from most other brands in a few hundred miles.
They last longer than the others (though I have still put holes in many pairs) and as mentioned have the warranty. I prefer the fit of Smartwool but still wear almost exclusively Darn Tough for the durability.
These really are amazing! I went full smartwool after getting a pair for hiking. I never looked back!
Wool poncho for cold seasons is also amazing, it's like wearing a duvet.