It's hard to compare The Book of Boba Fett to the Mandalorian because we have seen two full seasons of Mando. The story for Boba is still building up, but the production quality and nostalgia of returning to original era Star Wars is strong in both series. Maybe wait until Boba has finished to decide whether to jump into the full series. I would watch both seasons of the Mandalorian first. It's not yet known exactly how or if the two series will intersect.