Better off not buying the BTO from Apple. First, I don't think they offer a 500 GB 7200 RPM option, second, because you wouldn't get to pick the drive manufacturer, and third, because it's more expensive.
Buy the smallest hard drive possible from Apple, and separately purchase a 7200 RPM 500 GB drive. FWIW, I'm pretty sure the Seagate 7200.4's outperform the WD Black's.
The bonus is you slap the old HD in an external enclosure, and you've got a time machine drive! All for less than the BTO would have cost you.