I think it depends on where you would want to take these pants. If you're just hiking in cold weather and could use them in camp and you put them on in your tent or in cold but ok conditions, for sure the lighter ones.
For very cold snow conditions or winter mountaineering where you go light and fast so need to keep moving too, I would want the side zips. It can be hard enough to take some food out or adjust your crampons with your hands turning very cold in a minute. Those temps on a ridge or top of peak and putting off your snow shoes and boots, then putting on your down pants for me would not work.
I have separate rather heavy rain shell pants for the same reason too, with burlier shell material and full side zips so I don't have to undress to put them on. I have some ultra light rain pants from Montbell (used once) but I don't bring them on heavy snow mountain treks. I take the hit of the extra weight in those conditions.
Otherwise, for sure, I'd rather take the non-zip, light one. Good point about being lighter you're more likely to carry them.
edit - those Goosefeet look very nice, with opportunity to tune your fill and shell material. I would look at that, especially if you live in the States.