7D too heavy

There is nothing in the mirrorless crowd that comes even close in terms of focusing speed and accuracy. So if you need those qualities then you shouldn't even consider them. In terms of image quality there is another problem: The good lenses are as big and as the ones for the 7D - thus the smaller body only makes the combination a tad lighter and less manageable since the body then is too small to balance the lens.

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regards
Karl Günter Wünsch