On the front is far more practical for wired headphones. Plus you can always do something with USB-C pretty easily if you want to run it out of the back; if I had to choose a dongle for either fixed speakers or headphones, I’d pick them for the speakers.
It's definitely more practical for headphones. I'm curious as to why Apple decided to make this change now. Previous Mac Minis and the Mac Studios have always had them in the back. It seems uncharacteristic of them to go out of their way for wired headphone users after they removed the port entirely from the iPhone, so I wonder if it was a hardware/industrial design thing where it was simply more convenient to move it to the front for the new form factor.
Edit: also I noticed they moved the power button to the bottom corner of the Mac Mini! (It used to be on the back as well.) This makes me think even more that they didn't want to crowd up the back too much.
