The key factor is whether the chip is CMOS or CCD. CDDs are much better and have much lower noise, but I have never seen one in a cell phone. Usually with cell phone cameras the rule is the more pixels you have the worse noise you get, because there are only so many photons hitting the chip, so if you parcel the chip into more pixels and then increase the signal with an amplifier you get more noise amplified as well. So basically what Grossel said, better-larger lens will usually have a larger chip behind it. But with larger chip you need larger focal distance, so the phone would get too thick, so basic advice is not to think of a phone camera as a camera. It is like comparing a pocket voice recorder to a studio recording setup, so if you want a camera go get a camera, not a cell phone with a camera add-on.