I don't think it's Pead vs Richardson as much as it's Pead and Richardson.
S-Jax is one of the few remaining feature backs in the league. And he will only be around for another season or two. Once he falls off, we're most likely going to need 2 competent RBs in the backfield. Granted, Fisher has shown himself fond of the feature back, but I don't think that's the evolution of the game.
Hopefully, Pead AND Richardson can carry the load in the backfield.