Definitely go for the daughterboard, the edge connector is only to take 5V from your C64's user port to power the device. Personally, I'd do it a different way, but it makes it easy if you don't want to solder.
My solution: http://jungle.net/tone/uiecsd
Cool, again with the re-use of a commodore thing for another commodore thing.
So wonder if I would need this if I just use it for MSSIAH for midi stuff. If I save songs to the C64, then yeah I guess one of these options would be good. Hmm, which?