I have a 450D now with a 15-85. I want to replace the body with a higher quality sensor which both the 6d and 7d ii will have. I' mainly shooting landscapes and (safaris when i can...) of course we still don't know what the 7d ii will look like but but my doubt is between these two bodies. Both will be a leap in quality wrt the 450d. I have startex to sell my work and like to print at least at A3 size. Will a 24MP of a crop sensor win over a FF 20 MP?
Any suggestions? I can't really make up my mind...fortunately i still have time as the mkii still isn't out yet...
I doubt the 7D2 sensor is going to be radically better at high ISOs than the 70D sensor, as the 70D sensor was recently introduced and was a new design in itself.
In low to moderate light, the 6D will win this battle easily due to the FF sensor's lower noise at higher ISOs. In good light, it depends what you are shooting; for landscapes, the 6D will do significantly better and offers higher quality ultrawide lenses; but, for a safari, the extra reach and more advanced AF of the 7D2/70D will likely be more beneficial. The 7D2 will probably also have better weather sealing than the 6D, which could again be important for a less controlled safari environment.
If you are buying now, you also will likely pay a price premium for the 7D2 so it will be likely more expensive than a 6D.
If it were me based on your requirements, I would pick the 6D given what is likely to be introduced with the 7D2. It sounds like landscapes are your primary usage and the 6D with a EF 16-35mm f/4L IS has no quality focal length match in a crop camera like the 7D2. When you go on safaris, the 6D AF may be a bit more challenging and you may need to crop in post, but that does not sound like it will be where most of your usage will be.
For UWA landscape, here is an example of the best 16mm FOV equivalent on crop vs the best 16mm on full frame:http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=950&Camera=736&Sample=0&FLI=0&API=0&LensComp=949&CameraComp=0&FLIComp=0&APIComp
Another option might be buying both a 6D and a 70D - the 6D for most of your work, and the 70D for reach limited scenarios that also need more advanced AF like a safari might be. The 70D will probably be available for under $850 refurbed by the holidays, and the 6D comes up every few months for $1250 refurbed - the two together would likely be in the same price range of a single 7D2 at launch price. Plus it would give you a backup body and the ability to select FF or crop based on what your are shooting.