-- Last Updated: Mar-07-13 2:27 PM EST --
The Mini is a great kayak hauler. Current mileage is around 27/35, base under $20k. Has a low roof, back seats fold to give a lot of space. The Clubman is longer, has more space in the back, and the rear doors open to the side, which would be awesome, as the hatch on mine doesn't open all the way with boats on. It's not a deal breaker, though. I don't think the 4WD version is a good choice, as I hear it's kind of a dog.
Here's mine with a 24" and 24.5" wide boat on top: