Does the string output vary from pole to pole in various pickups?
The output can vary from pole to pole depending on the make and model of pickup and make and gauge of string. The pole height can play an important part in the balance of the strings. Typical Fender Stratocasters have staggered poles to balance each string but with modern strings, the balance is pretty equal. I like flat pole pickups such as the old Telecasters and Gibson style humbuckers. The quality of the string being used is very important too as well as the type wrapping used on the wound strings. I often leave the bottom E-A- & D strings on for a long period of time and more often change the plain G-B & high E. The plain high strings get pretty worn and I like to use new ones especially for recording and doing shows.