sorry man i can't really catch your ball, because i don't see why the a and d, in particular, should sound different..
but anyway alot of people like to refer to the j tone as 'throaty', p tone as 'growly' and other terms that we can't disprove, but to me it kind of sound like a kind of clipping. the p 'clips' at the lower frequencies and the j at the mids
and it is that characteristic that i love, so its roundwounds for me, with a mid boost on the eq. it gets even better when i solo the bridge and roll off the tone. the strings on my bass are some heavy gauge shit from fender japan that i have never changed, and i occasionally give it the stringlife treatment to keep em bright and defined. so dull sounding isnt really for me