There is no comparison between McCain and Kerry. I'm not a big fan of McCain politically, but as far as I know, McCain did not exaggerate his exploits like Kerry did, nor did he come back to the U.S. badmouthing other vets.
As for as what he did under duress while at the Hanoi Hilton, I'm not about to judge him for that unless there's evidence of some wholesale sellout. Everyone cracks under torture, it's just a matter of time. Real life isn't an episode of 24 and no one is Jack Bauer.