OK, I can now compare my Neve sweaters to the Ibex Shak.
I've got two Neve sweaters--the Larissa and the Annabelle. I wore the Annabelle home for Christmas and got many compliments on how nice it looked. Both of these fit the same. I also got the old version of the Trudy; I love the design, but it is cut much, much smaller than the other two, and I am going to have to send it back. I wear a large and it fits like a smallish medium, I think.
I also got a black Shak full-zip on sale at REI. I'm wearing it today for the first time.
The Neve sweaters are a looser knit than the Shak, and feel a bit heavier. They're fuzzier due to the looser knit, and much dressier looking than the Shak. The Shak is very comfortable, but I think the pocket zipper makes it look pretty casual.
Size-wise, the Shak in a large is just a bit tighter than the Neves. Weirdly, the full zip Shak in a large fits me the same as the Shak jersey in an XL.