I do sometimes wonder if you tend to adjust your style to suit your gear, so when you get a new pup you don't perhaps play it the best way, with the best settings etc.
Just a thought, but I know I felt my Nailbombs seemed to be better the more I played them, or maybe you just start to be able to pick out the differences. The pups I replaced were not bad pups, so the difference wasn't starteling, but the more I played the more I noticed the qulaity and clarity of tone, the way they broke up as I added gain etc. Buy the end of the week the difference felt more pronounced then the day I put them in.