p/s going to coolant hose?
Yes, oil to water type heat exchanger is more effective at transferring heat per unit area / flow rate.
But a big cooler with good airflow will also do a good job.
And if you're water temp is 200F and you want your power steering fluid to be cooler than that (I don't know what a good target is) then that won't work.
Also won't help you if your engine cooling system is close to its limit.
'Dreamin'

