I think Canon really built this 6D for rebels user upgrading to FF. Cheapest option to me is used 5d (2005-2008). But I need movie function for my 3yo daughter (my reason for 550d), so 5d is out. (d700 too)
5dm2 should be enough for me (mostly took Landscape & Portrait Photography). My only concern is 5dm2 AI Servo AF when taking candid photo of my daughter. With my 550d, keeper is very low. I think 5dm2 got little advantage with additional 6 AF assist during AI Servo.
Then came 6D,
-with native ISO 100-25600 (as 5dm3) compare to 100-6400 in 5dm2.
-centre cross AF f5.6 and vertical line f2.8 compare to centre (f2.8 line and f5.6 line) in 5dm2. (as i only use centre point only).
-AF -3 EV compare to -0.5 EV in 5dm2
-AI Servo with tracking sensitivity as 7d, 5dm3 compare to default in 5dm2
-AFMA with wide and tele value each for zoom lens compare only 1 value in 5dm2
and I plan to get the basic flavor with no gps, no wifi (cheapest maybe?)
And for all this reason, i cancel for jump ship and looking foward for full real world review of 6D.
PS: table that i attach in my 1st post is from here:http://www.canon.com.my/personal/products/interchangeable-lens-camera/dslr-eos/eos-6d?languageCode=EN#specificationAnchor
So i'm so sure 6D will sell with 3 flavor !!!