I'm a big fan of the Qoob chip (mainly because I have it) - its dvd upgradeable, just put the bios file on a disc and drop it in, it also has a built in FTP server for backing up your games - installation is pretty easy (I'm pretty sure its only 6-8 solder points). Mine's treated me well so far...
The upside to a case that fits regular dvds is just that - you can use regular dvds... however, the cube will only use 1.4gbs of info even on full size dvds, and for the cost of a full size dvd case, you can pick up like 50 mini dvd-rs, so you decide - I have the ICEcube case from xecuter - great quality, but mainly just for looks - I do have the advantage of full size discs, but then again, its not very cost effective.
I know there is a way to softmod the gamecube using a memcard and action replay, but the chip will more than likely bee cheaper.
Good luck...
On and on one last note, you will need a Broadband adapter to backup your own games.