In comparison, both shows are great. Both shows have a dads that most of the time don't have a clue and wives that make excuses for their behaviors but still love them more than anything. Both shows also have 3 children involved and a pet. They both seem to be either middle or lower middle class families.
The contrast for the two shows would definately have to be the type of humor used on the shows. The Simpsons has more a an entire family appeal to it while Family Guy has a lot more adult humor that parents today don't want their kids to watch or be subjected to. I personally don't care that my kids watch either one of the shows because they know that they are just TV shows and that behavior on TV is not to be repeated in real life. Meaning, I teach my kids whats acceptable for them to do and say and what's not.
If I had to choose which show is funnier, I'd have to say Family Guy, but that is just my opinion. I just haven't seen The Simpsons in a while and Family Guy makes me laugh no matter how many times I watch each episode.