Well, here's my take on the question.
From a consumer standpoint, there are certainly similarities. But from an operational management standpoint, Vail Resorts and Alterra function very differently. That's also reflected in how the Epic and Ikon passes are set up.
VR owns every resort on Epic except Telluride. VR does everything in-house, including software development and how their RFID system works. That's all proprietary. If a VR GM wants to buy a large piece of equipment, the choice of manufacturer is limited. When VR buys a resort, or set of resorts, there is often a fair amount of change in senior staff and managers.
Alterra has partnered with other companies from the start. The most obvious partnerships are with the Ikon Partners that are independently owned such as Jackson Hole, Alta, or Taos. Other key Ikon Partners are owned/operated by the other well known multi-resort companies: Boyne Resorts and Powdr. In recent years, Alterra has acquired companies that support the ski industry such as Aspenware. Aspenware provides software to ski resorts, regardless of ownership. Alterra resorts operate differently from each other. When Alterra buys a resort, people in leadership positions are usually asked to stay.
Going to Snowshoe or Solitude or Winter Park, someone who doesn't know they are owned by Alterra would be unlikely to guess those resorts had the same owner. Nor do most customers care. When I went to Mt. Brighton (little hill near Detroit), even though it felt different from Vail and Beaver Creek, the signage made it clear that it's part of the Epic "family" of resorts. The pictures on the wall outside the ski shop even included Perisher in Australia, along with big resorts in N. America.
This is the first time I've had an Epic Pass. I've been going to Ikon resorts for years, both those currently owned by Alterra and Ikon Partners. The difference is noticeable to me.
When listening to Storm Skiing podcasts with GMs for VR resorts and Alterra resorts, the differences in management style come through clearly to me. Same for interviews with VR or Alterra executives.