I like Young. I think Zito showed a lot, but wouldn't trust him yet. He ended the last 2 months of last year with a mid 2 ERA I believe, but it was in August that he posted a terrific ERA while September was around 5. Just pointing it out because I know a few people who have picked him up by looking at the last few months as a whole, not broken down.
I would go with C. Young 100%. He looked great against Arizona (in Arizona). Plus he'll get all those games at SD. Not to mention his numbers were awesome before getting hurt, and he seems to be back to form now.