Regarding the connection, the USB 3.0 is faster that firewire. in a ideal enviroment, the 3.0 goes up to 5 G/s and Firewire goes up to 800 Mb/s.
The drive will depend on your needs. if you dont have a usb 3.0 and you have the a firewire available on your computer, then the drive for you is the Studio that comes ready to be use on a Mac computer.