Just went trough the HRD apex 1 -> HRD Force 1 upgrade, and my friend is running HRD Rival 1
-There is rather significant step up from apex to rival in terms of the rear mech. Then the force mech is marginally faster / lighter on its own. However using a XD driver with the full pin cassette after the standard shimano/sram sprocket is yet another jump.
Serious gram saving can be achieved here, the low end 1130 11-42T cassette is 540g while the top 1199 is only 270. Also the XD driver is lighter.
-Brakes are technically the same, levers itself are alu -> alu+reach adj. -> carbon+rach adj. Calipers are different a bit, saving a few grams only. Didn't notice any difference in braking power.
-On the Apex the crank spider is integrated and alu. Rival is still alu but with swap-able spider, force is carbon (and the same as the Force 22, only the livery is different)