Taking the physical into account is looking at it in hindsight with 20/20 vision in regards to the trade. I would agree with you if I looking at it from a context other then the Jets trade.
Before that, Suggs HAD been injured, but it wasn't known by the Jets that he would fail a physical, and in their position, he had more upside then Gates or A-Train. The risk is that he was oft-injured and might not ever reach it. However, in college, Suggs proved that he could be a very good starting running back.
High risk, high reward, yet at the same time still low cost. If he fails to live up to his pre-injury status its no big deal.
Gates and A-train both don't fit what the Jets were looking for, and the Jets most likely wouldn't give the Bills much, if anything, for either one, seeing as how one of them is going to be cut in all likelyhood.