Both will delay the speed of execution.
Thread.sleep () : It will stop the current (java) thread for the specified period of time. Its done only once
It takes a single argument in integer format
Ex: thread.sleep(2000)- It will wait for 2 seconds
It waits only once at the command given at sleep
SetSpeed () : For specific amount of time it will stop the execution for every selenium command.
It takes a single argument in integer format
Ex: selenium.setSpeed(“2000”)- It will wait for 2 seconds
Runs each command after setSpeed delay by the number of milliseconds mentioned in set Speed
This command is useful for demonstration purpose or if you are using a slow web application