I think you guys are forgetting one main point: This is his first trip out west- from OHIO (no disrespect). So basically any mountain he goes to will be better than what he’s ridden, even if he has taken trips to the east coast.
With that being said, Utah wins mainly because it is super convenient. I have 2 trips planned there this season (one with the wife and one with my brother). Like others have said, you roll over and you’re on a mountain. That’s hard to beat.
My fav order is: Snowbird/Brighton/Solitude for riding. The problem for you is that your mom isn’t a skier, so the Park City/Canyons or SLC would be better for her. My recommendation is to take the bus to the mountain and let your mom stay in SLC or park city area to shop/sightsee.
As far as the riding, Snowbird definitely has great steep runs that will make your butthole pucker up, but I just love getting lost in the trees in Brighton (literally). Solitude is solid as well, I had more first pow “flip” (I let the front of my board dip into the snow causing me to flip head over heels ) so it will always have a special place in my heart. TBH, Park City/Canyons wasn’t anything too special. It felt like I was riding in Vermont (killington). When I go back this year I’m only going that way the first day to get acclimated and take advantage of the free pass they give you. I mean, they are good mountains, but they’re expensive and didn’t offer anything new (btw, I had no guide to show me “the goods”). Wherever you decide to go, don’t disappear. Be sure to come back and share your adventures/knowledge with the community.