It is like asking, which is more reliable Ethernet 10 mbps or 100 Mbps.
The material use to make CD and DVD are the same, the technology to storage more info in each one is different.
The long life storage, will depend on a couple things, the quality of materials used to make the DVD and CD, and how well you take care in protect them to storage them.
For capacity, DVD are way much better than CDs.
Just make sure to use brand name DVD,. To certain extent that will warranty the use of good material in making the DVDs.
How long they last?, well I hear around 10 years.
Now the technology to be able to read them, after 10 years do you will think will be around???
JR