I'd stay away from rechargeables. The problem with a rechargeable unit is when you are out and about, and then the batteries run down. I have used rechargeable D batteries for mine, but they don't last very long.
only good advantage to the azoo one is it will come on automatically.... i have a few friends that run these on there tanks with sponge filters... just has a preventative incase something goes wrong and they are not home...