It's not necessarily "tied to" an Epic mountain. It's all about which mountain you prefer.
If your favorite is one of the above, it really doesn't matter what IKON options are 'superior' or not. Which IKON mountain is "superior" than Stowe? Bush?
And what if your favorite mountain is Okemo? Does it matter Killington/Pico is "superior"?
Of course someones favorite mountain is up to each person and what they personally consider superior.
I would guess though that more people not tied to a specific resort through property or otherwise, would think that the Ikon selection of mountains in New England are better resorts overall than the Epic selection.