I think of the "NPS to Pure Nickel Transition" in these terms:
- Pure nickel has a lower output, generally. Of course, factors like core wire etc probably have a big impact, but when going from NPS to Pure Nickel I usually hike my pickups up a little to find the "sweet spot"
- Pure nickel will give a little less treble and high midrange. This makes them seem "darker" when swapping from NPS, but really I think they just aren't "hyped" in the high end. To me, it sounds like the center mids and low mids of Pure Nickel speak with a little more authority and the highs are chilled out.
NOTE: The GHS Balanced Nickels have a very sweet high midrange, but nothing like the presence of, say, DR Sunbeams. The GHS also mellow nicely over time.
The GHS BNs would be a great first step into pure nickel, IMO.