What do you think is the best cast size for the games you�ve played? What are the factors that go into your answer: genre, play group, gaming system, etc.?
Smaller is usually better but let me clarify it in a more mathematical equation.
Your cast size should be proportional to the milieu’s population of NPCs, be they created by yourself or your players. It’s much alike the idea of “faculty to student ratios” in schools and campuses. The more faculty there is per student, usually the more attention the student receives, and usually, on average, the better the student performs, all other things being equal.
RPGs work the same way. Having a target rich environment is crucial to games which go beyond a simple hack and slash. Players interact with each other, but they need a world to relate to as well. It makes what they do matter if they have people to share it with, or help them with it, or even oppose their goals.
Thus, SB, with its large cast of PCs, has an even larger set of Non Player Characters that for some players *make* the game. Jayson would not be Jayson without the triangle of Cyllene, Dulcinea, and Syanda. Lots of people play off of other characters, and there can be a sense of a struggle sometimes when there aren’t enough in a particular area to go around. And I think that I personally have trouble sometimes when there isn’t a large cast of NPCs available to toss toward a PC.
With all of that said, my con games usually average around 4-6 people. I have gone larger, and smaller, but that’s the size that hits my GM sweet spot comfort level. Logistics can get hairy with larger ones. One needs a truly epic cast to deal with a large game, unless the PCs are in of themselves just going to be interacting with each other and no one else.