I've spent a lot of time switching back and forth between CoRD and RDC over the past few months. Advantages of each, imo...
CoRD
- Allows you to connect to more than one host at a time. RDC does not.
- Does a better job of saving passwords. I connect to two different machines, both with the username "Administrator", but with different passwords. CoRD allows me to have a different password for each "Administrator" and remembers which host they go with. RDC thinks "Administrator" is just one user, so it tries to use the same password for both hosts. It works on one, but prompts me to re-enter it on the other.
RDC
- Seems more stable. For some reason, I never lose my connection with RDC, but do once in a while with CoRD.
- Seems to use more Windows interface features, like right-click/drag. That's something I really miss in CoRD, and on Mac in general.
My solution: RDC is always connected to my Windows computer (which I use instead of Win/Parallels). CoRD is also installed, but I only use it to connect to others' computers, and our Web server. They're both free, so why not?