I've had success with depth.
That being said... I just lost my first home game in several seasons to a first place team that has almost no depth to speak of
(13059727). That team has by far the best starting lineup in the league. Notice in my loss in 2OT, his starters posted minutes of 56, 50, 55, 50, and 58 minutes each. The rest of his team played a TOTAL of 21 minutes combined. (For those interested, 3 of those players had Strong game shape, and 2 had Respectable at the time.) I'm not sure how exactly his players all managed to play so many minutes with getting too fatigued. My players had generally better game shape and even my bench players would be starters on many of the other teams in my league. I could blame the new game engine, but I think this shows that as long as your players do not foul often, you have a good trainer, (and I presume his starters must all have phenomenal Stamina!), you can also be successful with star power and little depth.
I'll still go with my depth, though. I think my historic record speaks for itself.
Don't ask what sort of Chunks they are, you probably don't want to know. Blowing Chunks since Season 4!