Is there an actual advantage to BBP vs SBP?

I've never had an issue with the center register on an aftermarket wheel. Most of them, if not all are not hubcentric. On factory wheels you may have to occasionally have them opened up, however I've never used a factory wheel on an Abody so I can't say for sure. On my Volvo I bought hubcentric adapters and ran corvette wheels so again the size of the factory register really didn't matter.