I would do this trade.....I think the other guy is trying to warp your mind with the good players here but I think it will work out for you. I mean Gore is a beast and they will run all day in SF and K.Smith is great and should be in for a fine year as the "Lone" back in Det and TO.....don't know what to expect from him in Buf.
On the reverse.....Portis is a top RB (has injury issues but who doesn't right?), and MBIII (F.Jones will steal some carries but MBIII is the running game in Dallas) and BMarsh (has issues and that's the only thing that scares me so....watch out with him but I seriously think by the time the season gets rolling then Marshall will want to play and will get his act together) and then LJ is a throw in (he could possible come back into form as well)!
So.....I would make this trade but Bmarsh is the scariest part of it!
Standard H2H 12 Team 1 Pt PPR, Start 1QB, 2RB, 2WR, 1 FLEX (RB/WR/TE), 1TE, 1K, 1 DEF