Joe just got a new iMac and wants to know what external hard drive would be best use as a back up, USB 3.0 or Thunderbolt? Leo says that Thunderbolt drives are few and very expensive. He doesn't really need that. USB 3 is more than fast enough and very affordable. And they're formatted to be read on Mac and PC.
This Western Digital 2TB is perfect. He should get it with separate AC power, since Bus powered or PC powered externals will be slower. Leo also advises using SuperDuper as his backup option that can be used in concert with Time Machine. The benefit is that with SuperDuper, he can make a bootable backup just in case.