As noted above, FiOS offers superior
quality on its SD and HD channels. If you have a 34" screen, you may not notice a diffference, but if you have a 55-60" display, the differences are very obvious. FiOS HD provides significantly more detail and significantly fewer compression artifacts. Much of that pixelization you see on DirecTV's HD channels during movement simply doesn't exist on FiOS.
On the other hand, DirecTV's DVR is superior. DirecTV"s HDTV DVR has a 250Gb hard drive and better software. See pictures of the current FiOS software here
. The FiOS DVR has a 160Gb drive. Because FiOS SD and HD channels are higher quality, they also consume more bandwidth, and hence more space on disk; as a result, you are lucky to get half the storage on the FiOS DVR that you get on the DirecTV DVR.
FiOS has just begun to roll out improved STB and DVR software which makes their boxes more competitive in terms of features and usability; the new software is currently available only in parts of New Jersey, but it will be rolled out to all markets by April. Some screenshots of the new UI:
You can see a few more shots of the Verizon FiOS software upgrade at about one minute into the first video linked here
FiOS expects to support external SATA drive storage on their boxes in Q3 2007. If you want more storage on FiOS now, you can always buy a Tivo Series3 with a 250Gb, 500Gb, or 1Tb hard drive.