Comparing camera performance with low light and action

You try them out. Capturing action can be very, very demanding. A Nikon D4 is $6000 and it "only" has 16MP. A Nikon D800 is half the price ($3000) and has 36MP. One very big reason for paying $3000 more for a D4 is 10 frames per second with auto-focus. This is to say that any camera on the market is going to be a compromise to achieve a certain result. You need to find the camera that meets your criteria. Low light and action shots are not the strong points of a P&S camera. While I am sure some do better than others, it's like comparing the gas mileage of tanks. Is the fuel saving really all that different? But if you are just looking for test results, you can compare cameras here as well:

http://www.dxomark.com/index.php/Cameras/Camera-Sensor-Ratings/List-view

>Also, I was wondering how aperture size and sensor affects action photos and motion blur. Is a camera with a fast shutter speed the best way to capture action, and you just have to look for a camera with enough light exposure from a wide lens and a big enough sensor to be able to capture that brief amount of light coming in through a fast shutter

EV (exposure value) will be EV regardless of the camera. If I hold a light meter up to my subject, I can get an EV reading. Which means I need a certain combination of ISO/Shutter Speed/and Aperture Value to record an image. The EV isn't going to change because of the camera or sensor. Yes, you need a fast shutter speed to freeze motion. The faster the subject is moving, the faster the shutter speed you need to freeze the motion. The faster the shutter speed you use affects both ISO and aperture because again, the EV doesn't change. You might now need a higher ISO (how does the camera do at higher ISOs). You might need a wider aperture (will your lens have a wide enough aperture). Or, you might need to add light to increase the EV value. The usual advantage to a larger sensor is better high ISO performance. If you need ISO 1600, then you need ISO 1600. Now it's just a matter of how well your camera records an image at ISO 1600.