They both are better!

SBC is smaller, lighter, more parts available, fit into smaller places, generally cheaper. Generally will turn more rpm

BBC can provide huge cubic inches, more total power, can provide lotsa power without being as radical, generally will make more torque. Has more visual impact.

Not sure I agree with drg84 about Big Blocks being just for racin'. You can run a fairly mild big inch big block on the street and be really quick with not too tall a gear. To keep up running a small block you will have to either build it more, or run steeper gears.

Either way it's nice to have the choice

Pat