Is there an actual advantage to BBP vs SBP?
Wheel choice for the most part.
With the SBP stuff you need new wheels or adapters. Quality adapters are not cheap.
with BBP stuff you needs, axles, brakes and wheels. Worth every cent IMO. Switching from SBP to BBP is one of the first things I do to an Abody. IT allows me to put a decent fitting and looking set of wheels and tires on and upgrade the brakes. My current car came with drums up front so it made sense to upgrade those anyhow.