I have a WD portable hard drive that I used with my PC. It worked fine for me, but I have read online some problems people have encountered with these.
And if you read reviews of any of the other Manufactures, you would probably (i would say definitely) read similar reviews ........ Its "Murphy's Law" with "The Law of Averages" that says certain amount of things will fail, if a certain number is made.
Its been said above but any *good* brand will do you fine. I use WD because i have never had a failure, but the biggest thing for me when i 1st bought one, was the fact WD was a plug and play type.
Meaning i didnt have to do any partitioning or formatting. Plugged it in, started
SuperDuper and backed up and all done in 18 minutes.....
On backing up are you using ONLY Time Machine ??? If so I and all posters above would recommend using SuperDuper ^^^ Link or
CCC~CarbonCopyCloner. These both do a bootable copy of your HD as where TM doesnt ..... Just FYI is all and a little more help into your new Mac
Cheers