Helloo. I can't say I've tried the nickel ones, though they seem like they'd be fantastic for 'sticky' yarn that wants to cling to needles. I have a set of the harmony wood sock DPNs as well as size ten DPNs for big hats. They are fantastic. The wood is nice and warm and they slip and slide like wow. They're definitely luxurious.
I love the harmony wood, that's for sure. Also, unlike 'hardwood' DPNs, I've not had a single break.... yet. *knocks on needles*