It's something you might like to test, but I doubt you'd see any improvement. I'm being a bit vague because it's hard to say how manufactures may choose to handle the smaller resolution; if they choose pixel binning wher the output from several photosites are averaged (which may happen at high ISOs) then you may effectively be shooting at a reduced resolution anyway (even if they fudge it back up afterwards) or they may just be sampling the extra pixels out. Either way, it still doesn't change the physics of that tiny sensor.
In a nutshell, camera sensors are kinda like a DSLR sensor, but with most of the safety margin removed. Try to recover a badly under-exposed shot to see what I mean - I had to work on one the other day, and it was not a thing of beauty
PS: Nigel - sorry to hijack the thread a bit here - I can split this off to a seperate thread if you prefer.