Not sure about the full frame argument. What is it you're trying to achieve over a cropped sensor?
Lack of obsolescence, primarily, though the results from the colleague's 5D I borrowed were stunning - whether this is because I had more pixels to play with, better focussing, different DOF, better glass (a 24-70 in this case), I don't know. I just think it's the way things are going so am hesitant to buy another cropped body or more short-focus lenses.
If your needs are primarily long telephoto though (mine are not), it's a slightly different argument, since I acknowledge you can achieve the same effect with smaller and lighter glass.
But instead it just kept on raining
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