I have no preference on these two motors. I am a D-Series lover, and I have a b18b1 in my hatch.
As far as $ for $, you have to look at it this way:
For the b18b1:
~2,500 for the whole swap, and about 120 whp.
Turboing the d16z6
~1,500-4,000 for a turbo setup, and anywhere from 120-160/170whp if well tuned and its a decent engine.
Another thing to think about, you can spend the extra 600/700$ to build the z6 and have yourself a d-series beast. 400whp has been achieved on d-series motors. I dont know why everyone doubts them.
I would personally turbo the D. A turbocharged car is soo much fun. I wish I would have turbo'd my D16 now. Could have it built by now.