Pretty much night and day difference. Jackson Hole is a big aggressive mountain. While it has runs for everyone, it's definitely a mountain that will test the best. While the resort has its own base area with lodging, restaurants, etc., it's a good distance from the town of Jackson.
Park City offers you three world class resorts (no snowboarding at Deer Valley). Both Park City Mountain Resort and Canyons Resort are amazing mountains with great diversity for all levels. PCMR is located right in town, Canyons just a short free shuttle away. Both have their own base areas.
Depending on time of year, $300 is going to put you in low to middle price range. Won't generally put you right at the mountain but you can get something decent in close proximity.
You will find significantly more activities in Park City than Jackson. It will also be a ton easier to get to from LA.