This year I would pick Taos for its above average snow vs. likely below average at Big Sky. Also for late March Taos is predominantly north facing. Big Sky, though colder, is mostly south and east facing though Moonlight Basin is north facing. Both Taos and Big Sky/Moonlight are somewhat limited at the advanced intermediate level but very good for experts.
Taos is a unique and interesting ski town with its Southwest/artistic/Native American culture. If you're in town you'll probably want to have a car for getting around and because the mountain is a 15-20 minute drive up from town at 7,000 feet to ski area at 9,200. There is lodging up there if you want convenience but beware if you're more altitude sensitive than normal.
Big Sky is a fairly typical ski resort with lots of ski-in ski-out hotels and condos, so probably more convenient overall. Base area is at 7,600 feet.