I've got some of the grid capilene they're now calling capilene 4. I like it quite a lot but it's not nearly as warm as the old polar weight which was a very warm light fleece. The new stuff is more comfortable over a wider range and seems more comfortable when damp as it stands away from the skin. It's a significant improvement over the old mid weight capilene. The new stink control treatment seems to work ok. The stuff wears well and packs down well.
I like lighter wool underwear and particularly like an old set of two layer underwear with the wool on the outside layer. That was the best wicking baselayer I've ever had. Even though it was two layer, it was about midweight.
I haven't used the heavier merino stuff you can get now that you're looking at. I don't think you'll be disappointed in the capilene 4. Enough guys on here sing the praises of the good merino wool so I suspect you'll be pleased either way.
