Just by looking on the outside, I don't think you can tell which is which. One of these boats is a drag runner the other is a circle runner, if you don't already know the boats, can you tell which is which?
http://www.***boat.com/image_center/...411sangers.jpg
Besides the above mentioned differences, the quickest way I've found to differentiate them is that the circle runner has a slight V in the hull where the turn fins mount under the v-drive. The drag runners pad is flat until it feathers into the forward portion of the hull.
I believe the one on the right is the circlerunner.