actually in this case, both were running semi-similiar turbos, but the difference was, the guy running 300 whp on 8 lbs had a fully worked head by portflow....

LS heads are severe bottlenecks when it comes to shoving air down into the combustion chamber

in honestly
it all depends on your goals and the money you have to play with....

do you want mild power? 200 whp? 300whp? 400 whp?
300-375 whp is the limit I believe on a built d series, while its been proven 1.8 b series motors can get up to 500-600 reliably, with piston, rods, a good fuel setup, and a good manifold and turbo

Yeah I know when you boost you must have atleast the hack for it to work (as far as I know). Why are people using SAFC and VAFC and runing 8-10 psi on thier cars....I know it isn't the majority but some people are doin it...or am I just misinterepretting them?

By the wya, I really don't know much about the LS/LS-VTEC because I never really wanted that as an option. IGO4BMX, what do you think is the major downfall (besides having one cam ) to the D16 and boosting?

well
having one cam is an issue.. you can't really adjust cams effectivly like in a b series, besides shifting the power band...
second, d series motors have small bores, which is a problem since the sleeves literally shift under heavy cylinder pressures (thus the headgasket issues).
Also keep in mind the rod/stroke ratio is high (just like LS motors), which is why it makes alot of torque too. However too much torque and revving real high will destroy the sleeves (in which case you can get a sleeved motor)

If you tune a car correctly and don't run half assed fuel systems like the hack, emanage, etc., you can make plenty of power on d-series engines. Here is a recent graph of a stock sleeve z6:

http://forums.evans-tuning.com/viewtopic.php?t=3083

Basically you have to ask yourself what you want out of the car. Are you trying to get down the 1/4mile in a certain amount of time? If that is the case, d or b can get you there. How fast you go depends on how much money you invest, who builts it and who tunes it. Daily driver? Either engine can make 300whp on stock blocks, pump gas, which really is plenty for a street car. The nice thing about D series stuff is that if you pop one, they're super cheap to replace. On another note, the guys over at Epic Tuning in Allentown have gone 12.04 @117 on a completely bone stock z6 in an EF hatch. Granted this was on slicks, but the car was only making 308whp/262 tq. So in the end, the choice is up to you.