Although I do vote on one, I do believe these are pretty pointless.
I remember a few years ago, the local rock station did the same with several classic bands. When it got down to the last two, people were getting angry about results saying so-and-so is better than so-and-so and NOT being nice about it.
They decided to do a second one immediately afterwards using aLL THE SAME BANDS. WTH? Do to the conflict created from the first one, the top two were the first ones voted off second go around. Basically, they prove nothing and provide poor entertainment for the bored.