Both of these PVR work exceedingly well. I've owned both. They fundamentally have the same feature set -- with a handful of differences here and there. I think you'd be happy with either one.

I characterize the difference between them in terms of the interface. The ReplayTV feels more like it was designed by computer interface designers: very thorough with lots of search options.

TiVo feels more like a consumer electronics interface: somewhat easier and clearer to use with slightly less flexibility in the search set.

Ultimately, my wife and I decided we preferred TiVo. I sold the ReplayTV on eBay.

The biggest difference would be if you had DirecTV. The integration of DirecTV and TiVo in a single receiver is an incredible advantage in usability and the most desirable setup of all, IMHO.

But I think you'd be very happy with either unit -- and they WILL change your life. The PVR is the best home electronics device I have EVER purchased.