DVD case advantages:
They are cheaper. New DVD cases tend to run about $0.20/case while new jewel cases tend to run about $0.40/case.
They look good. I think DVD cases look better on a shelf and there is more room to show artwork on the spine.
DVD case disadvantages:
They are larger. They will take up more room on a shelf than a standard jewel case
You need artwork for EVERY SINGLE game you own. Even if you have a game CIB, you will need to find and print a cover for it to convert to DVD.
I prefer to use original jewel cases simply because I don't want to replace all of my original covers. Most of my PS1 games don't have DVD artwork yet and it will take a lot of time and work to get all of them done. Plus, I don't know where I would store my original jewel cases if I switched to DVD cases because I certainly wouldn't get rid of them.
Also, there is one other 5 disc game. I don't know the name of it, but it was a Japanese dating sim that used the extra discs to have the girls call you by your actual name. At least that's what I learned on the PS1 episode of Game Sack.
