What are the key differences between fink and macports?
Fink is a binary distribution using tools that originated from Debian (e.g., apt-get, etc.)

Macports is built around the philosophy used by the FreeBSD ports collection. In this you download tarballs directly from the upstream source, apply patches and compile. It's entirely automated.

I haven't used Fink in quite a while (since Panther) because it didn't seem very well done to me.