The F3R is meant to be more rugged: it has an additional feature to protect against vibration, and a five-year warranty, which is more common in the enterprise sector of the market.
The Caviar Black on your page is "recertified" - it broke, it was returned, they fixed it, then they sell it used. The guarantee is only 90 days.
So: How important is a guarantee to you? And since the guarantee is a half-decent indicator of durability, how reliable a disk are you willing to pay for? I have a bad habit of moving my PC while it is running - I might spring for the F3R. If you are better than I am about that, and only move the machine while it is off, pay less for the F3. If your business depends on this machine, or you run it in a pickup truck while driving in the desert, spring for the F3R.