The BB is a much stouter package as far as the skirted block and 5 bolts/cyl instead of SB's 4.

There are a few guys that have been very successful with fast SBs, though, so it's not a cut/dry rule.

But in an A-body, I think a SB is much more likely to reach completion and be a better-engineered package on the first shot.

consider also that if you get 200 more HP from a BB it means nothing unless you get it to the ground, so there's more weight and expense and chassis setup.

K.I.S.S.