@Pan Michał: I've expected something more from you than writing "I'm wiser than you" and leaving.
I was writing fairly long reply post, but something broke down, so I'll do it the short way...
I am not smarter than you, nor am I dumber than you, if you felt like me saying that, I'm sorry. Unions between Poland and Lithuania differed from that with France because of main cause (leaving aside smaller). KoP and GDL in their personal unions stated (and fulfilled the statement) that Kingdom and Grand Duchy are separate states, yet they share the same goals/politics and they shall operate together for mutual causes, and further tightening bonds between themselves. Union with France stated (and fulfilled the statement) that Kingdom of Poland and Kingdom of France are separate states that do not share same goals, thus one partner won't get involved (or won't do anything to involve one another) in another's external (let alone internal) affairs.
I'm sorry, I really won't go further in the discussion, because I was asked to, wrote the above because you said you've felt like being ungallantly leaved.