Re: Why do we still have an output difference between neck and bridge pups?
I don't like calibrated sets, myself. It makes bridge pickups too beefy sounding and/or neck pickups too weak. I want my bridge pickups to be very bright and my neck pickups to be warm yet articulate when needed. Output matching is not as much of an issue to me, and imbalanced outputs can be mostly dealt with by adjusting pickup heights, or by just learning to use it and play around it. The balanced output thing that has become the norm alters tone in a bad way IMO. It takes away too much treble from bridge pickups and gives them too much bottom end for what I want from a guitar.
I have often used two pickups that were intended for the neck position in order to have what I consider a guitar that sounds "right." I do this with the P Rails (two low output models) and with the Parallel Axis (two neck models), and in the past I've done it with '59s, PGs, and SNSs (in which case you get something a lot like T Tops).
IME, using a stronger bridge pickup magnet and a weaker neck pickup magnet, without over or under winding in one position or the other, is a better approach to balanced output, because it doesn't screw with the tone nearly as much as under or overwinding.