During sales, Best Buy's prices do become more competitive with the online retailers. For example, during the week of Feb 18 - 24, the hard drive in the first link (160GB SATA) was selling for $59.99 ($79.99 - $20.00) at my local BB. The second one (320GB EIDE) was going for $109.99 ($154.99 - $45.00). Prices do fluctuate and are sometimes different from their online store compared to the brick-and-mortar (B&M) ones.
Aside from getting trained staff to install the drive(s), another advantage to a B&M store is you get to take home the merchandise right away. Plus, if someone screws up, you get to yell at people to their faces instead of someone in a call center miles and miles away.