Since I have the NEX 5, I have put my A900 too much on the side... reason: portability ... and video. But ... I was thinking about if I should not bring my A900 in my Very low light rock band photography due to the fact that the NEX is now very good at high ISO.
The question was: For a same 14MP from the 24MP of the A900, is the NEX even better than the FF sensor. I know some people will say : ok but the answer is easy the file of the NEX is near than three time smaller than the size of the A900...
On the left NEX, on the Right A900 (reduced to 14MP). NO NR applied to both, JPEG straight from RAW in LR3.2.
Complete Large and crop image here if you want to do your own tests. I have also included upscale NEX 5 pictures to 24MP. http://www.pbase.com/nadeauf/nex5_vs_a900_highiso
So ... the answer to my question is that I should continue to use for the moment the A900 for my most of my serious shooting, even in very low light condition. Yes, there is a lot of lost of detail in the A900 sensor ... but my test results seams to shows that It is not loosing enough detail to switch camera body for ISO3200. I'm mostly using ISO4000 and 5000 usually in low light Bar environment where there is a kind of big difference compare to ISO6400 in noise. The 14MP of the NEX seams to shows less noise at ISO6400, but there is equivalent details. I might have took a ISO5000 and ISO4000 to compare ... next time