Haven't played BB, finished SotE last night.
Overall, I much prefer the scope and scale of Expansions like SotE for RPGs, they last long enough to tell a proper story and actually expand upon the base game in a meaningful and lasting way. Think Far Harbor vs Automatron if you've played Fallout 4.
Pound for pound, I do think SotE is better. Midir and Gael were fantastic, but the overall package wasn't quite as nice, nor as expansive.