In the end it depends heavily on what activities you’re doing, what temperatures and weather you’re looking at, and how much you’re willing to spend. I call wool the best all-round fabric, and I’ve never noticed a particular difference in synthetic base layers. You really should be focusing on material more than brand. In my experience, the difference in the brands tends to be cuts, range of thread weights, sizes, quality of stitching, purity of fabric (“pure merino” doesn’t mean “pure merino” unfortunately) and price of logo (both UA and Icebreaker make you pay heavily for the right to wear their brand).
Those look like a good pair for general winter survival, skiing and other low-aerobic activities, or for something like hockey, where you’ll sweat mightily but will change as soon as you’ve finished, but if you’re exerting yourself in cold temperatures, and have to hang around in those temperatures afterwards, I’d really look into wool. If you’re sticking with synthetic, I find Patagonia has a great selection of capilene (better than UA’s polyester, in my opinion,) at prices comparable to other high end synthetics (or low end wools. Merino has the same properties as conventional wool, but it tends to be less itchy and it more commonly cut into styles appropriate for sports.
The only drawback (besides price) for merino is that some people with enormously sensitive skin still find it too itchy, though I find it perfect and more comfortable on my skin than synthetics. Comfort is something to consider as well. Whatever you do, try on this pair before you buy it.