Snort,
I have and use both. I've found that each one has strengths and weaknesses. Often one will be skimpy or not even cover some repair, but the other will! I read the sections on a particular repair in both manuals before I start the job.
For example, I like the Haynes Electrical diagrams best, but the Chilton's has other illustrations that are better.
My advice is to get both, you'll save far more than the cost of both on your first repair! But... If I had to have only one, I would have to choose the Haynes.