Seagate Portable Hard Disk Help Me In Purchasing A New Portable Hard Disk Drive !?

Help me in purchasing a new portable Hard disk drive !? - seagate portable hard disk

I want to buy a portable hard drive 500 GB
The main objective is to establish a backup of my data in large

KNW shud I go out .. ? What brand is more reliable

and work without a problem exists

Products that are already on my list

1) Western Digital Passport Essential
http://www.wdc.com/en/products/Products. ...

2) Transcend StoreJet 25M
http://www.transcendusa.com/Products/Mod ...

3) Seagate FreeAgent Go
http://freeagent.seagate.com/en-us/hard- ...


PS - I would like to know also used, what kind of rope in external hard drives, an external power supply (if they buy a hard drive). Are they connected directly to the outlet or joiining with the cord on the CPU?

Help me, please ... Thanks