Hi, Awipsuser
There are some pretty good reviews and comparisons online. You should be looking for reliability. Check which brand's drives are considerate more reliable. Both devices offer USB 3.0 and some utilities. The WD My Passport has a SD card slot. Since you need the drive for long usage, you should check some battery comparison, but I should warn you that those could be not so accurate.
Whatever you choose, make sure you use it as a backup destination. I mean, do not put your valuable data only on one device.
Hope this helps