If you're only going to Osaka, nowhere else, it's not worth getting a pass. If you will be traveling within Osaka and using the subways and private railways, you might want to get a Surutto Kansai debit card, but that's not from JR. You just buy it at any subway or private commuter train station.
Otherwise, look up Hyperdia and figure the fares for your planned trip and compare them with the prices of the various passes.
