8.4/10.0 120lb can carry gear. For a 160lb rider spring will be soft.
8.6/10.3 140lb Rider can carry gear. For a 180lb rider spring will be soft.
8.8/10.5. 165lb Rider can carry gear. For a heavier rider the spring will soft.
9.0/10.8 175lb Rider can carry gear. For a heavier rider the spring will be soft.
9.2/11.4. 190lb Rider can carry gear. For a heavier rider the spring will be soft.
9.4/11.4. 220lb Rider can carry gear. For a heavier rider can carry luggage but would have to add preload to spring or adjust fork height.
The 9.6/11.4 may be a better choice especially if your aggressive.
Aggressive riders that carry speed getting airborne off road go up a spring rate if you want more bottoming resistance.
Reviews
Huge difference I’m a heavier rider around 250 so I went with the 9.4/11.4 in the rear and with the.67 in the front well worth the money eats up the bumps drive's like a dream