The thing about concerts is they are notoriously dark, although the musicians are frequently well lit. Don't get hung up on who has the most megapixels, in fact that is almost the opposite of what works well in the dark. To gather the most light in the dark you want BIG pixels. For the same size sensor, the one with higher megapixels will have smaller pixels. Bigger sensors are better.
You can't really trust the manufacturers when they try to brag "my camera goes to ISO 12800 or 25600". It can go that high, but it's just a setting on the camera. It might look like crap above 1600.
One resource I pay attention to is dxomark.com. Here is a page where I selected 3 cameras from a list. I don't know anything about these particular cameras, I just grabbed one each Sony, Canon, and Nikon for demo purposes.http://www.dxomark.com/Cameras/Compare/Side-by-side/Sony-Cyber-shot-DSC-RX100-III-versus-Canon-PowerShot-G1-X-Mark-II-versus-Nikon-Coolpix-P340___957_941_939
Below the cameras are 4 blue bar graphs for each camera. The bottom bar graph shows "Low Light ISO" with 495, 581, and 273. They run some standard test on all these cameras, and decide that each camera can obtain a certain high level of clarity with low noise up to this ISO. The number doesn't mean much except it gives you an idea of how well each one does in the dark relative to each other. The difference between 495 and 581 is 20% and probably not visible, but the difference between 581 and 273 is more than double, and that is significant. By comparison my Nikon D700 has a rating of 2303, and the current state of the art body is the Nikon D4S at 3074, for something like $6000. Anyway, if you are comparing different cameras, I think it's worth a few minutes to look up on DXOmark.