I love 1st party N64 memory paks. Why? Evertime i have mine around other people, "what the hell is that?". Apparently nobody knows what a real n64 pak looks like...Interestinly enough it DID corrupt a couple times...but it fixed itself. That rules. I think it might eb dying now or something though, I can't seem to find my old goemon save.
Generally I don't see a point to the 3rd party cards anyway with a few exceptions. AR type stuff that lets you save to a harddrive is fine, since you can take it off the card and have it stored even safer-ly, as long as your HD holds out. The saturn 4-in-1 AR is awesome for various reasons, and I tend to keep backups of my saves on it. I don't expect them to stay for all time though obviously.
DC memory you really don't have much of an excuse to buy 3rd party since VMUs are awesome and dirty cheap, and the official 4x cards don't cost much more either. Cube cards, I just buy the black ones used. 10 bucks usually, that's a good deal. Sony cards seem terribly overpriced to me, I still don't own a ps2 card to call my own. Now that I think about it the one i generally use might be 3rd party, i'm not sure. It seems stable enough so far though. I'd LIKE to get a card but what, they're like 25-30 bucks? Jeez. I'll wait for the Hori ones to show up maybe and get orange or camo...