So sometimes these two elements of RPs are in direct conflict and my question is which side do you come down on?
Not in terms of prefering character driven or plot driven RPs but more would you betray the actions your character would take to advance the plot or are you more likely to jeopardize the plot for the sake of staying true to your character?
Those are the more extreme ends of the debate so you don't neccesarily have to come down one or the other.
My answer would be I used to try to never compromise my characters and if some one tried to force me to make them act differently I'd argue it and failing that leave the RP. I'm not as extreme as all that any more but I think I still come down quite firmly on the character side.