[ford38v8]

Chris, the roadster is the preferred for a definite style advantage. If you would base a decision on the roll up windows of the Cabriolet, then you miss the whole point of having a classic example of Early Ford. The door roll into the cowl and bright windscreen frame makes the whole design really come to life.
Then, some base their decision on the numbers: The Roadster had a very low production number, I don't have access to that number at the moment, but something like just over 600 worldwide units. That in itself makes it more desirable, and the $ numbers should rightfully follow.