In general, economic conditions and factors are more important. This is because they set the bounds of what is even possible in the negotiations. It is typically the case that no bargaining behavior can move the negotiations out from these bounds.
A good example of this would be the deal made between the "Big 3" automakers and their employees' union, the United Auto Workers. This union had in the past gotten very favorable terms from the auto companies. But now, with the companies having needed bailing out by the federal government, it was clear that economic times had changed. This meant that no type of bargaining behavior on the part of the union was going to be able to get the sort of contract the union could once have gotten.