EOS

[cicopo]

Another big difference between crop bodies & full frame is the depth of field each delivers at the same aperture. The same lens at the same settings gives noticeably more DOF on the crop body than on the FF body. That can be important for those who prefer fast glass shot wide open to isolate their subject.  

[Scatterbrained]

A crop sensor gives you more "effective" reach. Which is really what matters. Ask any birder and they'll tell you, it's all about pixels on target.