Ratchet straps are much cheaper, and a few feet of pulling is all I need.
You might be confusing rated working load with the actual ability to pull. The comealong has a much longer lever arm and is therefore better suited to manually pull loads. The ratchet strap, on the other hand, is intended for transport. It's designed to handle dynamic loading of cargo on trucks, etc.
The bottom line is that they serve different purposes and you should select the one that meets your functional needs the best.