I've hauled bikes, kayaks, canoes, etc for years. Have tried all kinds of carriers. In my opinion, for bikes, the best are hitch mounted racks. I was a die hard roof top guy for a long time until I came around. Hitch rack for the win. Easiest to load/unload bikes. Easiest to remove the rack. Low air resistance when loaded. Many advantages and few disadvantages. Just my 2c.