Hello all Shop Botters

My name is Renato and I am kind of new here on this forum.
Even though I have never used a CNC I've been working with 3D modeling per about 12 years now.
I attended the Shop Bot camp last month to learn a little more about this nice machine and see if it would match my expectation.
Now I am getting realy close to place my order on one Buddy Alpha 48"
The question now is which spindle should I get the 2.2 hp or the 4hp?
What would be the advantage on one 4HP spindle over of one 2.2HP
Any suggestion would be appreciate