Hello
I'm gonna sell my 70D soon and wonder what you should have done in my position.
I got two ideas that I want to share and see what you think are best for me =)
Idea 1:
A new 6D with 40/2.8 + batterygrip for 2350 USD
Idea 2:
A used 5D Mk2 (1250 USD) and 1D Mk2 (mint condition, 10k shuttercounts) or 40D with batterygrip (mint condition) (both 600 USD/each) all these used cameras has 6 month warranty. So together it will be under 2000 USD.
I want 1 full frame and one Aps-C/H camera. I photograph mostly wildlife but I'm gonna photograph more nightlife and landscape in the future. I don't need high fps in my camera, I want good AF and good ISO handling. The animals are mostly static.
Should I buy a new modern FF camera and save for a APS-C instead of buying two used cameras directly?
but for now, in my situation, it's best to buy a new 6D 
