If the main criteria of buying new FX camera for landscape photography is low sensor noise, what camera do you suggest to buy (Nikon): D800 ~2.5k, D600 ~1.7k. Does it make sense to pay extra money for this, if noise is almost the same, if it's true?
All large sensor cameras top-notch for landscape photography because no matter which, noise is extremely low around base ISO which is what you will be most likely shooting at. From a tripod I might add, which is essential to get critical sharpness.
Noise being the same at such low ISO setting, what you are left is the question of resolution which depends on how big you intend to print. If large, the D800 is certainly worth the money. If not, then getting the D600 will probably afford you a better lens which is even more important when it comes to sharpness.
The one thing you did not mention which is important for landscape is dynamic-range. The D600 has a slightly wider DR than the D800. So, if the resolution is not an issue for the print sizes you make, I would strongly consider the D600 instead.
Considering how close the noise performance of those two cameras are to each other, I would think the very significant difference in resolution would be a more important consideration for any serious landscape photographer.
Deciding between the D600 and D800 based on noise performance at low ISO is like comparing two sports cars based on their braking performance:
- The 2011 Corvette Z06 Carbon edition stops from 60 mph in 93 feet and can accelerate to 123.6 mph over one-quarter mile in 11.6 seconds
- The 2010 Porsche 911 GT3 needs 94 feet to stop from 60 mph, but needs 12.2 seconds to accelerate to 116.7 mph over one-quarter mile.
At 123.6 mph, the Corvette can travel an additional 108.8 feet in the extra 0.6 seconds it takes the Porsche to reach one-quarter mile. Which is more significant? One foot of difference in braking performance or 109 feet of difference in acceleration?
Just like the two cars in the illustration above, both the D800 and D600 are high performance machines. They are both capable of taking very good landscape photos when used to their full potential. This includes both being in the right hands and having the right glass attached to them. If you are concerned over a 0.2 stop difference in noise performance at ISO 100, then surely you would see the much greater benefit of a high performing prime lens such as the Zeiss T 25mm f/2 ZE or the Nikkor 24mm f/1.4G ED over the Zoom-Nikkor 17-35mm f/2.8D IF-ED you mention in a comment to another answer.