I was initially thinking of getting the canon glass 17-55 f2.8 IS and the 70-200 f2.8 IS, but it appears as if Nikon has seemingly the same lens values in their line. Any experience on which will be the better glass? If they are the same, seems as if it will be cheeper to go the Nikon route so as to avoid the higher priced Birger mount. Any comments would be greatly appreciated.