I really like "Live at the Apollo" from 1990 a lot, BB with big band backing from the Philip Morris Superband. For the most part, when it comes to the post-Kent material, the live albums are best. I assume you already know about "Live at the Regal" and "Blues Is King".
I bought all of the albums he made in the late 60's and early 70's after seeing him live for the first time around 1969, including "Live & Well", "Completely Well", "Indianola Mississippi Seeds". While each of these has its moments, ultimately I think as whole albums they are weak at best, misguided at worst. The long jams are boring, the guest stars are out of place. BB works best with his regular band in front of an audience, and when all is said and done, this is how I want to hear him.
One of the greatest evenings of music I can remember was BB live at the Hampton Beach Casino in 1992. I had seen him several times prior to that, but was absolutely on fire that night.