I find in general that WD is easier to deal with than Seagate IF you should need to warranty the drive for any reason.
And while data loss is always a concern should a drive fail for ANY reason
you should never put yourself in a position where a single drive failure
can cost you any data that you really care about.
That being said the "My Passport" drives are intended to be "portable"
and they are generally built around what amounts to a "notebook" HDD
Generally speaking 3.5" drives are more reliable than 2.5" drives.
Also Generally speaking external drives built around 3.5" desktop drives,
like the WD "My Book" series tend to be less expensive than the more portable "passport" drives as well as more reliable.
Lastly if you really "NEED" 2TB you don't want to buy a 2TB external
you need to buy a 3TB External.
Buying on-line the best prices are likely at Newegg, though recently I've seen
WD and Seagate Externals at competitive prices at my local Walmart.
2TB "My Book" at Newegg for $109
3TB "My Book" at Newegg for $139
$30 more for 50% more capacity.
Comparison shop before you buy.
Oh... one other thing the Seagate "Backup Plus" drives have included software that blocks some utility programs... for example I have a 2TB backup plus sitting here that is not "seen" by any of my Defragmenting programs.