Hi, and welcome to the form.
I don't think you can go wrong with either option. If you like the look of the cheaper one it seems like a pretty straightforward choice. Depending on where you order it from you can always return it if it doesn't work or is poor quality. Even though it's shorter it still supports the GPU 75 percent of the way, which is sufficient for it's intended use.
Looks like that card comes with a support bracket. Based on quick Amazon search the reviews on it's effectiveness is mixed. Either way, you may just want to see how bad the sag actually is once you get everything built, then add a different support bracket if necessary. Unless you're also going for looks with it, then have at it!