Here is an article comparing the 2
don't get me wrong, I love my Z, and in stock forum it will run circles around the mustang in a canyon cruise. On the other hand, I've owned 4 (modified) mustangs, and for very little money put into a few upgrades they can really shine. They really are a lot of bang for the buck, I beat the crap out of those cars and was really surprised at how well they held up to the abuse. Anyone that would disregard the 2011 Mustang with 400+HP as not being a real competitor, obviously lacks experience. We all know you can make any car go fast and handle good, it just takes money.
Not planning on trading in the Z anytime for a 2011 mustang though.
2010 Ford Mustang vs. 2009 Nissan 370Z Comparison Test on Inside Line