pwp said:Negligible or zero size advantage and a big dose of buyers regret.
Plus having multiple systems sucks.
There is a point to running multiple systems. I do. But these systems have to be complementary. Sony FF mirrorless plus Canon FF DLSR is NOT the way to go about this. A lot of Canon users are being tempted along this path.
It makes more sense, just to give one example, to shoot with medium format plus a Canon DSLR. MFD is just too slow to shoot action with, and is heavy. Alternatively, you can shoot FF or MFD, plus APS-C. You get more reach with APS-C lenses (e.g. for wildlife), or else it is just more portable for on location work. It's also better to shoot with dedicated APS-C lenses rather than mounting FF lenses on an APS-C body: you just lose too much resolution otherwise.
But FF mirrorless and FF DSLR aren't as complementary in most cases as it is made out to be. That's why I made it a major point of the post to avoid going down the path of adopting Canon lenses on a Sony, and to stick with native lenses. Others have come to the same conclusions: