Nicholas & mt12345
It's quite simple. Just answer a question - do you want to be mobile or you prefer to stick with desktop system with chances to expand (PowerMac). As much as I love MacMini (I used to own one) I switched to PowerMac as I can put in better GFX card than Mini had, I can put SoundBlaster (with line in which Mini doesn't have), couple of hard drives etc..
I also have PowerBook awaiting for MorphOS release for it. I like to be mobile as well.
We should be happy that MorphOS Team gave us plenty choises about HW.