Going for D600 or keeping mirrorless for the GH3?

I don't think I've got the right experience to give you an informed answer. I shot a lot of Canon for awhile (APS-C) but it was all zooms and I didn't explore their prime lens line up at all. I don't have much direct experience with Nikon since the film days.

If you want an uninformed opinion (i.e. mine) if I were to enter FF right now I actually think I'd go with Nikon. Canon sensor tech has stalled for years now and I'm more impressed with what Nikon is offering for FF. That's probably not the right approach though, probably the right thing to do is look at the lenses available and decide based on that. And if you already have lenses for one system or another that would be another factor (I no longer do, I sold all my Canon L lenses earlier this year).

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Ken W
See profile for equipment list