I also believe that the situation was avoidable. When Shane and Otis both went into the medical trailer, I immediately knew that it was going to be a mistake because there was no one outside to arrange the escape. That's one of the things that I think makes Shane more of a "villain," it's not just that he'll do whatever he thinks he needs to do to survive or help Carl and Lorie, it's that he's reckless. Instead of making a plan ahead of time, Shane just charged in, and when push came to shove, of course he fed Otis to the zombies.
They don't really compare at all, except that Troy was probably better. And not nearly as painful to watch either. Both were about the same length as well. EDIT: Here's my official review of the movie- http://www.hybridmagazine.