A desktop dropcatcher sends requests through a registrar's API , which is not as fast as the registrar sending their own requests to the registry.
You are usually allowed to send 1 request every 1 or 2 seconds, while Dropcatch , Pheenix etc send thousands of requests per second. So your chance to beat them to a name they are actively chasing would be less than 1 in 1,000 , I would guess closer to 1 in 10,000.