Last time I looked, MacPorts had a more paranoid approach to dependencies. That can be good and bad. Homebrew can be easier to use, until you run into a corner case that trips it up. MacPorts can be frustrating in how many dependencies it will insist on installing its own version even though the system-provided version might have worked.

I've gone back and forth. For a while homebrew could install a working GHC for me while I wasn't having any luck with MacPorts. Later something else caused me to switch back to MacPorts. Neither is perfect. Even MacPorts only allows dependencies at the package level, without regard to variants, or versions, if I recall correctly.

There are some variant packages, eg, php5.2.x vs 5.3.x

For those of us who haven't hit homebrew's edge cases in years of use are probably fine to keep using homebrew. If it ain't broke...

I just want it to install packages. It does that so I'm happy.

Familiarity in my case -- for my legacy Mac servers I'm sticking with what both I and my boxen know. :) New servers will all be running Linux, so it'll be with the package manager for that distro, likely Debian.