From what I've read, when all is said and done if there is a sale, the authors will get about the same amount of cash either way, and the consumer will pay about the same amount (as long as you're willing to accept: $10.00 ~= $15.00), so the real difference is how the money in between gets distributed. And the only way to "punish" either corporation for their childish behavior would be to stop buying books altogether, which would end up also punishing the authors and inflicting self-punishment on the readers.
For better or for worse, at least I can be unbiased in this. I had interviewed with the part of Amazon that makes the Kindle (and for a while thought I'd done pretty well). Had I ended up with that job I'd probably be at least a bit more on Amazon's side.