Fink has been around since at least 2001. Fink and MacPorts are package managers that want to be "orthogonal" to the system, that is, they install their own version of
perl, libraries, compilers, etc. in own trees (/sw for Fink, /opt/local for MacPorts). The reason for this is that they have no control what Apple does with its software, and it occasionally broke things when Apple updated their own stuff.
From what I understand, Homebrew wants to be more "integrated" with the system, uses the libraries that Apple provides, and installs its stuff in
/usr/local/bin and other standard folders. I guess that means that the software choice is more limited with Homebrew, I can't imagine that one could install KDE with it, but I've not tried that.
One point for Fink vs. MacPorts: a few years back, the Fink project provided binary packages; that is you could download and install the packages without compiling them yourself. Its package manager still has that ability, only there have been no binaries available for a long time. I do not know if that has changed in the meantime.
So in short: without the binary stuff, Fink and MacPorts are very similar. They should have more packages available than Homebrew, while Homebrew should take less disk space for the reasons I stated above. Concerning the quality: I've never installed Homebrew, and between Fink and MacPorts I usually prefer the one that I'm not currently using.
So if you are satisfied with MacPorts, just stay with it.
P.S. The reason I never tried Homebrew is that I use some precompiled packages. These usually also install themselves into /usr/local/bin and the like, which just cries for trouble.