Looking at both hard drives, the Seagate 2TB Ultra Slim is a little bit smaller than the Transcend. Transcend is 5.16 x 3.15 x 0.98 inches, while the Seagate is 4.47 x 2.99 x 0.38 inches. The Transcend is also 3.2 ounces heavier. When it comes to reliability, I can't comment on that as I haven't used either of those. If you need more info, just go to the official manufacturer's website of each product you're looking at.