I can tell you from experience that a b16 "feels" heavier up front than a d16. however, the b16 feels EXACTLY like the D16 from 1k-5k rpm. The only fun part with a B16 is pass 5k and ask yourself, how many times in a day do you go pass that?
I was in a similar dilemma, where i could go b series and call it done but instead i stuck with a D series and did all motor. high comp, bored .20 over, lighten flywheel/pulley, high-rate valve springs, and a mild weber cam shaft. Of all that money i spent on it, i could have gotten a pretty gsr for it but i stuck with the idea of when/if i beat other people with a SOHC id get the face "
". none the less, it didnt work out, the A6 could only go so much before it detonated (no tune).
In the end, i bought a B16 + S1 cable trans and never looked back into a d-series.