The 7 open resorts, ranked by vertical, from least to most.
7. Sunday River...............560'
6. Killington......................591' (750' skiable from top of K1 to bottom of North Ridge, but can't be lapped)
5. Sauveur.......................603'
4. Gore............................733'
3. Belleayre.....................945'
2. Bretton Woods..........1063'
1. Whiteface..................1852'
A few points of note:
1. The 4 that have consistently, for years, tried to open ASAP, are Killington, Sunday River, Sauveur, and Bretton Woods. The latter two do not have downloading setups, and have to be open top to bottom, so they are rarely first, but are often the first to have top to bottom skiing. The 3 ORDA mountains are the wildcards. While they've always been willing to open earlier than their normally scheduled dates, they've never been in a situation where they had 3 of the 7 open resorts.
2. Sunday River, Killington, Gore, and Whiteface are using some form of downloading. Sauveur, Belleayre, and Bretton Woods have top to bottom skiing off a lift directly accessible from a parking lot.
3. Bretton Woods is the only open resort where you can lap a detachable lift. All the others are using fixed grips, though Killington, Gore, and Whiteface are using detachable lifts for downloading.
4. Sauveur is not the only open resort with night skiing, but is the only one currently offering night hours on certain days of the week.
5. I think Sunday River and Killington are in the bottom two slots because both resorts have downloading setups that use only a small portion of the resort's vertical. This allows them to consistently open earlier than the others, but that advantage goes away when they try to open top to bottom, and they are further delayed by how their snowmaking is phased. For Sunday River, top to bottom skiing is usually the second snowmaking phase, while for Killington, it isn't until the third phase. Both have to complete the earlier snowmaking phases first. Killington is further slowed down by World Cup commitments.