Depends. Say you want to run 15psi intercooled. That would put you in the 72%efficency range on B turbo and 65% efficency range on the A turbo. Thats using some standardized numbers, lots of assumption and a PR of 2.3 with 39.84 lbmin corrected air flow at 6500rpm.

However, lets do some more math and you find that at 5000 rpm with the same PR of 2.3 but a corrected 30.71 lbmin airflow that you are outside the surge line on B turbo and still well within surge on the A turbo.

More math shows that at 4000 rpm with a PR of 1.74(assuming a 5psia reduction in boost) we have 20.48 lbmin airflow which is still within acceptable efficency on the A turbo while close to the surge line on the B turbo still.

So basically, id choose A.