My thought was that a relative-pitch notation might present a steeper learning curve. But I don't really know.
I've worked with intermediate-level musicians who are skilled at regular sight-reading, but who struggle to learn to transpose on the fly. A relative-pitch notation might be like requiring everyone to "transpose" all the time, forcing them to learn this skill before they can proceed.
On the other hand, maybe you'd teach it differently. Instead of learning transposition as carrying around an offset to add to each pitch, you'd learn it as carrying around a scale to which the relative pitches would be mapped. I wonder whether this would be easier or harder to learn.
I've worked with intermediate-level musicians who are skilled at regular sight-reading, but who struggle to learn to transpose on the fly. A relative-pitch notation might be like requiring everyone to "transpose" all the time, forcing them to learn this skill before they can proceed.
On the other hand, maybe you'd teach it differently. Instead of learning transposition as carrying around an offset to add to each pitch, you'd learn it as carrying around a scale to which the relative pitches would be mapped. I wonder whether this would be easier or harder to learn.