Sous vide chuck roast or chuck steaks?

I've never cooked sous vide before, but am now equipped to try thanks to the holidays.

We have a 3 pound chuck roast -- I'm not sure what the exact cut shape is, but it's vaguely cube shaped. If we cut the roast into steaks (1-2 inches thick) before bagging and cooking, what effect would this have on the cooking time and/or quality?