Based on my experience, I recommend you get the the WD 1TB My Passport. I've had one of those for six months and it's been totally reliable. I certainly can't say the same for Seagate external drives.
When you plug the Passport in first time on any PC, Windows may pop up a driver error or "may not work properly" error.
Don't be alarmed, all you need to do is install the WD "SES Driver" from here: http://wdc.custhelp.com/app/answers/detail/search/1/a_id/5419
You don't need the SES driver to use the Passport drive. It's only required if you want to use the "WD SmartWare" application, but the only way to suppress the Windows error when you plug it in is to install the SES driver. otherwise the error will annoy you as it did me.