The idea was that the DS9 jumpsuits were Class B's... Since they were on a dirty, hardly functioning Cardassian monstrosity (which I love), they needed to be okay with getting their hands dirty. My thought about Generations was that Picard finally loosened up and let them wear some Class B's. I'm totally baffled as to why DS9 suddenly changed to the Class A's from the TNG movies First Contact on. But I liked it. As for Voyager wearing the DS9 Class B's... Well, how much actually made sense on that show anyway? Plus, come on, with as much holographic power they used (separate power grid... please) and shuttles they replicated, they totally could have gotten the FC uniforms too after getting in touch with the Alpha Quadrant.