seagate seems more reliable...here's why
aside from personal opinion, it is like this...Western Digital started getting into this trend of doing this and that, then they started churning out My Books. You can just do a general search on Western Digital My Book quality and you'll see why.
if you like a brand, that's fine you won't be swayed by varying opinions...but i experienced a WD my book lemon...did a search and came to the conclusion that they have high lemon percentages...the my book was my sister's thankfully (for me)
Live Search: western digital my book doesn
Western Digital My Book Pro Edition II sucks! at Tom Raftery’s Social Media
in the latter, you can see how many people have issues with WD.
Western Digital used to be bar none, "good" but now they are iffy. They spread themselves quite thin in my opinion. My internal boot drive is a seagate, however I do use an external WD esata/usb drive. The catcher is that it's WD inside, but it's a "cavalry" drive.
That is why I think WD has quality issues...a high rate of mass production with little QC results in lots of lemons.
BUT so long as any product has a decent warranty, go with anything