If you can get Mathews instead of Stewart, then I like the trade a lot more. Partially because I'm not to sold on Hightower for the rest of the season.
Seems to me like he is trying to secure SDs run game and I'm not sure he'd accept a Matthews trade. You could go for it, though. I think the Matthews trade is the better one for you. Not so much for him but maybe he's high enough on Hightower that he'll overlook it.
It looks like you both have Tolbert and neither one of you has Mathews, so I would stay away from this trade haha. But really though, I would keep Mike Williams, as I think he's the best player in the whole deal. Williams and J-Stew lose a lot of value with Cam Newton taking goal line carries away from both of them. An interesting guy to look at might be McCluster, since he has dual eligibility in some leagues. You seem thin at WR and to drop WIlliams for a couple RBs also seems unnecesaarily risky. Stand pat.
QB: E. Manning, Bradford RB: Peterson, Best, Tolbert, Starks, Torain WR: Wallace, Welker,Colston. P. Parker, Floyd TE: Hernandez, Davis K: Hanson DEF: Rotating