Beyond the ratings
Numerical ratings are great, but when two competing products both perform so well, it helps to have a little more information. Here are a few more things to consider.
Interestingly, many Replay buyers prefer it to TiVo because TiVo seems more corporate and advertiser-friendly. Sonicblue, Replay's original owner, went bankrupt, partially because of the financial burden of legal challenges from Hollywood studios and TV networks incensed at Replay's Internet file-sharing and automatic commercial-skip features. TiVo avoids controversy by simply not including those options.
TiVo also has the ability to suggest programs that you might want to record. We don't consider this a big deal since most people know what they want to watch and don't need advice from a machine. Then there's the TiVo Showcase, which is basically an advertisement on the front page of the menu. A recent showcase for The Lord of the Rings: The Two Towers included full-length trailers and the option to record upcoming Frodo-related shows.
The peanut gallery
ReplayTV user comments: Model 5080
TiVo user comments: 80-hour version | 40-hour version
Judging from the user opinions on the CNET reviews, both products will change your life. The comments for Replay, however, consistently complain of poor customer support. That's a major factor that we don't consider when reviewing consumer electronics products. Depending on how far you trust user opinions, you may want to take this into account when deciding between these two DVRs.
That said, both TiVo and Replay have unofficial online forums--such as the TiVo Community Forum and Planet Replay--that can help users in need. Seeking information from online communities is often faster and easier than waiting on hold for tech support.