I've done President's Day trips with my family both at Sugarbush and Killington, and in my experience Killington did a better job at handling the holiday crowds. It was much easier to avoid long lift lines at Killington during Pres Day weekend in 2019 than during the same weekend at Sugarbush in 2018 and 2017. I liked Sugarbush so much that I wasn't expecting to rank Killington as highly when I returned to Killington for the first time in nearly 20 years. But by the end of our visit last year, I felt that Killington had an edge over Sugarbush, for my taste. I did some mid-week skiing at Killington this year with a friend that only reinforced my positive impressions. There are lots of very nice and helpful staff to address questions, the lodge at Killington's peak is beautiful inside and is surrounded by stunning views, there are nice "entry level" trees for my kids (i.e. "Squeeze Play" and lots of fun unofficial glades off of some green trails) who then worked up to black diamond glades. Somehow at Killington we managed to always park pretty close to a lift (which is especially helpful with younger kids). All this being said, I'd recommend choosing Sugarbush if you haven't gone there yet. The views on the run from the top of Mt. Ellen are especially impressive. The terrain was fun in every category, and there were parts of the map I never got to explore. I was less confident in trees a couple of years ago than I am now, so I didn't sample them much. And I had to rule out Castlerock due to long holiday lines. We hope to return in late March, if the conditions are still decent.