Do I need a fast external or is usb 3.0 enough.

Hey guys,

I'm just curious on some of the speeds regarding external hard drives when mismatched with different usbs. So I've heard that a 5400 rpm external hard drive with usb 3.0 will be faster than a 7200 rpm external with usb 2.0. Is this true? Also, I'm assuming then that a 7200 rpm external with usb 3.0 will be the fastest option out there?

Thanks in advance.