I'm on the other side of this, I prefer David Johnson. I just think there is more upside, and a chance he could win the starting job, on a team that will have ions of garbage time. Bernard is a 3rd down RB only, on a team that will mostly be leading. I'd bet Johnson sees at least double the touches Bernard sees this season, and considering Bernard won't see GL work and Johnson might(though he also might not) makes Johnson my choice.
Basically, I see a similar floor, but more upside with Johnson.