I wouldn't count on DVD being anymore stable than CD.
If Sandi's description of the DVD manufacturing process is accurate, the 2 layers can separate too.

That's what happened to a lot LDs. Granted, one might expect LDs to be more susceptible due to their size/weight placing more stress on the bonding between layers, but that doesn't mean DVDs are not susceptible to different issues that might also lead to separation of the layers.
And if I had to guess, I'd think that the higher data density of DVD might make it more susceptible to certain things that can potentially ruin the dye, etc. since there is probably less margin for error w/ the higher density.
Hmmm... What do people use to store their CDs/DVDs for on-the-field use? Does everyone use hard jewel cases or similar to prevent flexing of the discs? I would not want to store them in a CD/DVD wallet/album for too long.
Anyway, whatever method you choose for on-the-field offloading/backup of photos, make sure you make extra backups when you get home.
_Man_