There's a huge difference. Honestly not a fan of the 8515s pickups, but the 5909 are one of my favs. They really aren't even in the same league. You'll be very happy.Thank you for the input, I now have the 59/09’s to replace the 85/15 S with just waiting on the 5 way blade to get the most out of the 59/09’s so I’m hoping to be able to head and feel the difference.!