I never was crazy about the Cape. Been there only twice, as recently as this past September, including Nantucket and Martha's Vineyard. Many moons ago we were there for whale watching out of Provincetown which I highly recommend.
In fact, I am not even crazy about coastal (or even inland) Maine. I am not sure why. I mean- I definitely don't like traffic and crowds. So that is number 1.
I agree with Panina- the Provincetown end of the Cape is really nice- all along the National Seashore from end to end (ends at Provincetown)- is really nice/interesting. That I did like a lot, though I would be worried about swimming due to sharks (there were sea lions close to shore when we were there. Loved watching them.) and the intense waves. And I am a person who loves to be in the water. But just being at the ocean on a sunny, breezy day was awesome as the Atlantic Ocean is intense. I do love seafood a lot also.
Maine to me is also crowded and traffic on Route 1- ugh. I did love Acadia National Park and Bar Harbor and also Camden. Stayed at the Samoset in Rockport.
But I really think it comes down to "vibe". A feeling. People ask me why do I love Vermont and I always say it is a "feeling". Nothing you can put into words. I love the big lake with the Adirondack views. I love the mountains and the cool air. I love the farms. (I live an an area somewhat similar in NY). I also like NH a lot- again- the mountains and lakes, the wilderness. It is like a more rugged version of Vermont.
Maybe it is the elevation in VT and NH. I don't know. But I love the mountains and the balsam smell and well- all of it. I love going in the crystal clear lakes with the mountain views all around me. Yeah- they are real cold- but a good floaty and I am only partly submerged and it feels great when the sun is out. I can stay out on the lakes for hours. And many of the state parks have small, sand beaches- good enough for our camp chairs.
We only live about 2 hours from the Berkshires but that area does not do it for me. It's nice, but I think it is boring. Once you do the main sightseeing that is it. Maybe because we live so close, but really we would just assume stay home. The resort we stayed in was nice- Vacation Village.
All this said-If you have never been to the Cape you should go. It is something to see and experience- the National Seashore. And take the speed ferries out to the islands (Martha's Vineyard and Nantucket). Get your tickets in advance on line to save time. We also got tickets for tours of the islands once we arrived as we were only there for the day and wanted an overview. That made things easy for us. Some people take bikes over or rent them when they get there. Some people, stay on the islands for a day or two.
As most places in the Northeast, you also can never count on the weather, so keep that in mind. It rained a lot when we were there, but it was an unusually extremely rainy year overall in the Northeast,