ant_riv,
The main difference will be is that the Z-coils are quieter because in effect they are buckers. It also of course affects the response and the Z-coils will have slightly less highs and more mids, but the difference is not too big; there will still be plenty of sparkle and no loss of quack in the middle positions. The difference is even less when you take into account that many of use playing an S-500 will have both PTB tone controls dialed back a tad
Just for completeness search this site for
"Will Ray bridge Z" and you'll find a number of posts discussing the advantages of using a WR Z-coil bridge pickup.
- Jos