I don't know why people are so hot on Howard. Yes he averages Xyds, and he also gets no yds a lot. His average gets spiked with the long runs, which he can't play out because he runs out of juice.
4 runs, 20yds, 2yd, 2yd, 0yd comes out to be 6yds which looks good but what it actually did was give you one 1st down and a punt.
Can you rely on him to get a 4th and 1 or from the 5yd line? No (but red zone is better than 4th and 1).
Keep him if we don't have better but he certainly shouldn't stop us from looking for better.
I don't know about Leno, I just know I want better at his position. If he can switch and upgrade someone else keep him.