Blue Origin says the BE-3PM engine in its New Shepard vehicle can throttle down to 18% max thrust.
Compare to 57% for the Merlin 1D engine in stage 1 of SpaceX's Falcon 9 (and to 39% for the Merlin Vacuum engine in stage 2, though stage 2 doesn't have to land, and its on landing approach that low throttle would most help).
So I'm wondering: What are the challenges in increasing throttle range, and what keeps SpaceX from matching Blue Origin's 18%?
The BE-3 runs on liquid hydrogen while the Merlin runs on RP-1. Does the choice of fuel account for the difference? And could it be the big reason why Blue Origin chose that difficult fuel for New Shepard?
There is some background information available in answer(s) to Do Blue Origin's BE-3 engines need to run for 7 seconds to "warm up"?