I had the same problem with my llano QZ after a couple years and just bought a Wilkin half-zip to replace it a month ago. I can't tell a difference in the collars or fit at all. I noticed two differences in the few times I've worn the Wilkin.
1. The Wilkin is a half-zip instead of a quarter-zip (like down to your belly button instead of nipple line on the llano).
2. The aerowool on the wilkin is noticeably lighter and more comfortable in hot weather.
With my limited experience, I am happy with the switch so far.
I have the Wilkin 1/2 zip and it is like a crew collar with a zip. My llano is a crew so I don't know what the QZ llanos collar is like but the Chama QZ has a collar that comes up 1 1/2" or so when you zip it up. Almost like a mock turtle neck.
Fit with the Llano and Wilkin are the same but the Chama is much baggier.