The " Best all around Powder for Sidekick/Huntsman" is a matter of personal choice.
I use two, T7 pellets under 240grain TC Cheap Shots or 240grain Hornady XTP's, both with the Hornady/TC black sabots in my Sidekicks/Huntsman, and have been very happy with their performance. In my guns, they both have the same POI, so I use the Cheap Shots more often to save money. I have used Blackhorn 209, and loose Pyrodex in the past, and have been also happy with their performance, but I just like the ease of reloading with the pellets. The most important thing to take into consideration is the particular brand of powders' performance in your BP gun.
I'm sure the other guys here, will chime in with their own personal likes and dislikes regarding the type of powder that they use.