For the first, panic, heavy brake event the determining factor is mostly the balance of clamping forces between front and back calipers. The 40mm rear does very well with the OEM front; actual measurements show 1.0 G braking. No prop valve change is needed. A BBK system "could" do better if you really, really dial in the adjustable prop valve. An ABS system "should" do better because it can adjust each tire independently compared to non-ABS when your foot only controls all four calipers as a set.
At some point, the heat generated from repeated braking will affect the brake pad effectiveness, so a larger pad is needed, meaning a larger caliper. Obviously the type of pad is important and with a smaller pad you will have larger temperature swings. Further, with the larger pad you would find more "race car" pad applications.
It all depends on use, aggressiveness and frequency. I've melted the plastic tire valve stem caps when the wheels positioned them above the 40mm calipers after a track event. Calipers were fine, pads go away quicker because they are smallish.