Aw, come on now - if it were a real fight, they wouldn't be able to balance up on the window sill like that :)  You can also tell it's not real b/c the little one is throwing all the punches.  When they're *really* fighting, she's running away and hiding under the bed.
                
                                      
Dang! Your cat fight has actual cat fighting!
I do like your orange cat. It'd be funny to see your orange cat fight my orange cat.