Its a tough choice. No clear player standing out. Both are on good offenses, both have divisions with solid run defenses. I think Perine has less competition for being the lead back. He was drafted for his potential, and Rob Kelley has performed well but is not a top back. Perine will get his chance at some point. And Cousins is mobile but quite a running QB.
Lacy basically has 3 other back competing with him, and a QB who can run. There is alot more competition for him to get touches. I had Lacy his rookie year and loved him. He’s great when he’s hot, but he hasn’t been playing his best recently. It depends on what you are looking for. Lacy will most likely get chances early on, Perine looks like he will have to wait.