I could not find any reviews to tell you whether one or the other performs better. They look to be much the same, except for the capacity difference.
One thing to keep in mind is how the unit gets power. The listings you show do not tell you this. MOST portable external drives like this get their power from the USB port they plug into. USB ports have a limit on how much power they can provide. Smaller external HDD's like this usually can get enough that way. BUT a few need a little more, so they come with a special cable that has TWO USB plugs on its end, and you MUST plug BOTH of them into separate USB ports on your laptop - that's how they get enough power, they use two sources. So IF that is what you buy, you will have to be sure you have TWO unused USB ports on your laptop.