Fuel distribution is probably better at higher RPMs WOT but what about low-RPM part-throttle, isn't the dual-plane better?
What I was getting at is I think the separation of the 4 cylinders to their own plenum has more of an effect on drivability than the slightly longer runners... maybe I'm wrong though my stock 318 came with the split-single plane 2-bbl intake and that obviously didn't have drivability issues.