With the release of Ocarina of Time 3D, a new "Iwata Asks" appears and deals about OoT development. They talked bits off the original game development line. Full interview http://iwataasks.nintendo.com/interviews/#/3ds/zelda-ocarina-of-time/1/0 Good reading!
64DD used magnetic disc? My question is. Why? They don't hold more than CD-R I think and were more than likely more expensive too. Appears Nintendo just used Odd formfactors (Cartridge when they were dead, magnetic tape and mini dvdr)
Yeah it definitely wasn't the brightest idea, I think the main factor was that you could write data onto the disc besides just reading it, allowing for content saving, dynamic changes to the world, etc etc, but it obviously didn't work out too well as a choice considering the system didnt make it to the states and the big titles all wound up getting dumped to carts instead
There's already a thread about this exact topic. http://www.assemblergames.com/forums/showthread.php?t=33480