When I changed from the guide R’s to the saints on my Rocky instinct, it totally changed the bike. So much more stopping power, could ride faster and slow down later. And never got forearm pump again. With the guides I had to be on the brakes all the time.SLX is the four piston XTR/XT design with some lower cost changes. Saints are a completely different package with forged calipers, etc that have been around for years. Zee's are the lower cost version of the Saints. BTW Saints are my favorite trail bike brakes by far.