What model 594 did you make the change on ?
AND ... the difference ???
Now I know , there is a tendency to find "night & day differences" , especially when we spent bunches of $$$ to do it, but as objectively as you can,
What are you hearing as a result of the change ?
I put the 58/15 LT in an S2 594 Singlecut. As for difference, the 58/15 LT definitely has better clarity than the 58/15 S. The 58/15 S is a warmer and lacks a little brightness and top end sparkle. Output is similar, but the LT pickups just sound better with a clearer top end. They sound great with my little Vox AC4 practice amp and with my Delta Blues gigging amp.