That's a great either or. I'd rather own Star Trek and JP to play. I'd do the Whitewater/Who Dunnit to flip/trade. You're getting a better deal on the later but I don't think those two games will have the same staying power.
I would want to keep Star Trek and White Water. I bet you could trade a Who Dunnit plus $1,000 and get a Star Trek. (or spend a little more and get a Star Trek premium). That seems more doable than trading a JP for a Whitewater.