Because of the way that DVD media is manufactured it looks like it could easily be more reliable than CD's Simply because the reflective surface is enclosed in the plastic and should not be prone to scratches or delamination.
However, their isn't much evidence to the length of time data will stay on a burned DVD disc reliably. My oldest discs are about 6 months old and they still work so that is a good sign... but I think we'll have to see the technology wait a bit longer before we can truely tell.
From my experience with CD burning I stick to Verbatim and Taiyo Yuden discs. cdrlabs.com often conducts burn quality tests which can tell you what media will burn with the least amount of errors with your burner. This may not equate to better longevity though.
On another note, one thing that I am doing to ensure the integrity of my DVD backups above and beyond CRC testing is to create parity archives, AKA PAR files.
The easiest way to think of it is RAID 3 for zip/tar/rar files. You basically create a parity disc that contains enough information about all your other discs so that if one of them dies you can recover the data from your parity file and remaining archive files.
For zip/tar/rar sets where files are similarly sized (IE, each file is 4.5GB excepft for the last file) I would recommend PAR1. Easy to create/recover in both windows and linux. PAR allows you to create recovery files based on your needs. If you want to create parity in case of 1 disc failure you'll end up with a 1disc sized parity file, if you want to have coverage for 2 discs failure it takes 2 discs worth of space for your parity file and so on. Remember that this parity file allows recovery if any of the discs happen to fail, so it is much more space concious than a mirror.
Right now I'm using 1 parity disc on my backup set which consumes 4 DVDs of space. If I grow to require 8 discs I'm pretty sure I'll find a larger media or crete 2 parity discs.