The Sony one lets you start playback as soon as enough data has been written to the disk, typically 1-2min after recording commences, or any time after. Great for ff through the ads!
Ours was state of the art when we bought it, but like all these things, has been eclipsed a bit. Same thing with double the HD capacity avail now at less $. The next big thing will be the blue ray laser system. Might want to wait for that? (Once the Sony/Toshiba battle over format is resolved. Seem to recall the same kind of battle re VHS a few years back.)