If you have a QR20, or 20mm through, the fork mount is a pain. But then if you have a really strange shaped frame, the fork mount is perfect! before I had my pick-up, I had a dual hammerhead fork mount on my roof rack.. looked cool riding down the street, and is a snap to pop the bike in. From what I have seen, the frame mount ones are a pain.... but work well with many different types of bike (As long as they are not strange shapes, or carbon-fibre... ).

Hope that helps a little!