I haven't tried either the Hi-Beams or the Sunbeams, but I play a set of DR Fat Beams on
my fretless, and they feel as well as sound great.
From what I've gathered about the other two models, the Fat Beams probably have more brightness than the Sunbeams, but more low mids (as opposed to high mids) than the Hi-Beams. Whatever. I'd guess that they
all work very nicely for fretless.
MM