If you carry for traveller the better is going to buy portable and power supply by USB.Here the new product by Lenovo ThinkPad 500GB USB 2.0 / eSATA External Hard Drive 57Y4400 cost ≈us$170.I'm using WD 120GB,250GB,320GB,500GB(cost ≈us$90-100) portable external hard drives almost two years get no problem.If you like you can try one of this WD brand.
If you just for home using you can try to buy a External Enclosures Docking Station Hard Drive system to run e-sata or usb 3.0 to transfer file,it's run more fast and the hard drive cost more cheap.