In terms of sheer power, the Mac Pro is by far the best. But you should look at your needs. Do you want the most powerful laptop, desktop, or all-in-one?
If you want a full-fledged desktop and have 10's of 1000's to spend, the Mac Pro is the way to go. You can still get amazing power and great specs from the all-in-one iMac. If you want a laptop, the MacBook Pro is the way to go.
Tappin and Talkin from my iPhone 5