Leshoure has just been too damn frustrating for me. I keep playing him waiting for his "breakout" and it's just not coming (or, we already saw it back in week 3...) I'm actually starting FJax (against HOU, of all teams) over Leshoure this week.
That being said, both these guys are the primary backs on their respective teams, so you are bound to get some decent points out of both of them. Jennings' upside is that he is essentially the only real threat on the JAX team, so he will get plenty of work.
I may just be "frustration-biased", but I'd say run with Jennings this week.