I don't think either choice is clear cut but I think Hightower has, with his limited touches, shown that he deserves a chance to carry the load. In his very limited time...heck, in just the last two games, he's made plays that I haven't seen Edge make over the last few years. If he's making a big play each game with less than 10 carries, I'm certainly curious to see what he could do with 20 touches.
I'm not saying bench Edge but I think the shift to Hightower should be explored. Edge, I think, should be the complimentary back to Hightower at this point. Much like Bettis was with Parker.
For a feature back that isn't being overworked, Edge's fumbles this year have certainly not been good for my perception of his value.