One of the more convenient aspects about PS4 is that you can very easily replace its hard drive. With 40GB+ installations becoming the norm this generation, it's clear that 500GB won't last long. Although Sony encourages hard drive upgrades, Microsoft does not. However, if you're willing to void your Xbox One warranty, you'll be able to rather easily replace your Xbox One drive.
A teardown by iFixit (via Engadget) reveals that Xbox One uses a standard 2.5" SATA II drive. Specifically, a Samsung Spinpoint M8 ST500LM012 500 GB 5400 RPM with 8MB Cache, which goes for $55 on Newegg.
Of course, the real question now is: what happens after you replace the drive? Will Xbox be able to boot without a properly formatted drive? While Sony lets users download the console's firmware update onto a USB stick, Microsoft does not for Xbox One--at least not yet.