Homebrew starts from the MacOS CLI apps provided through XCode. It's a usermode package manager built on top of XCode components. MacPorts builds everything from scratch, which grants more power and optimization opportunities, but comes with many, many more rough configuration edges to deal with.

The optimization opportunities for some packages are typically on the order of 2x-5x faster, which isn't enough to deal with the headache of extra config for a personal dev box. So, my rule of thumb is, unless I know exactly the performance trade off I am trying to take advantage of by going with MacPorts, I will be better served by using Homebrew. I will wind up spending more time fixing config then I will have saved on execution processing time.