Sorry, meant to jump in on this earlier...
I find that Rick necks feel different because the ones I have played are pretty wide at the nut - I wonder if that has anything to do with the perception that the necks are chunky? They don't taper like a Jazz or Precision. Just a theory!
I have found with my '76 4001, the pickups are pretty low output. Early on I put in Seymour Duncan pickups -
I had them out within a couple of days! Later on, I realized that though the pickups were low output, they sounded great. I don't know for a fact that all the late-'70s ones had lower output, but I have heard a couple of people say they had similar experiences.
My impression is that for many, the '76 is less desirable, but it also depends what you desire! For some, full-width inlays would be high on the list, for others a real horseshoe pickup. I really love my '76, but a lot of that has to do with the circumstances that resulting in my becoming the caretaker.