You can always tell when an apple fan is backed into a corner when they bust out the car analogies.
Just trying to keep it simple for you....
However, it's 20 years of real experience that tell me it just doesn't make sense trying to run a design agency or a print house on pcs.
It's no mistake that the vast majority of the graphic design industry run on makes, we need reliability and productivity. This is not always measured in pure speed.
Sometimes you need to look at how often machines crash (and yes macs crash too) how often do you need to get IT help (I never have needed it) how easy is the software to use (to me it is perceptively easier on the Mac, even though they should be the same they are not)
Obviously some of this is personal opinion, some is not.