On one hand, working for a supplier gives you a certain amount of security, in that your customer base is diversified, and you have a better chance of surviving a big industry shake-out. According to surveys I have seen in trade journals, suppliers actually pay better than OEMs on average. But suppliers can be harder to advance in, and often do not have as wide a range of projects to work on.
GM and Ford are shaky. Ford is known for treating its engineers poorly, while GM is known for a plodding, indecisive corporate culture. But you can advance quickly at Ford, which values gunslingers; GM values engineering and supports engineers to do good work. DCX is the strongest of the Americans, but isn't that much better off, really. Chrysler was not (in the past) known for excellence in engineering--more "get it done quick and cheap". Now they are known for repackaging old Mercedes designs.
These reputations may no longer be accurate. If any of my few readers are in the business, let me know in the comments what your experience is.
Mitsubishi is on its way out, it seems, like Isuzu, and would be a very risky choice. Nissan is owned by the French, ugh. Hyundai/Kia is up and coming, but much of its engineering is done in Korea by Koreans, I suspect. And the cars, zzzzzzz.
In general, the idea of working for a foreign run company leaves me cold, as if I am switching sides in a cold war. Even though the "American" companies are all global behemoths, which crap on their workers and suppliers to save a nickel, all the while wrapping themselves in the American flag.
Or would you try to get out of the automotive industry all together? You like the work, but the constant contraction and endless stream of bad news doesn't bode well for your future.