I think John is a better fit than his brother. John has won a Super Bowl so he's done it on the biggest stage. He has a team that has a core that is being changed right now and probably is going to be in a slight rebuilding stage over the next few years.
Obviously he hasn't done it at the college level before, but his brother has and what better resource is there than Jim? And his dad was a college coach for years too. So it's not like he doesn't know what to do.
Everyone makes a big deal about the fact that Jim is so resilient and is such a hard worker, but so is John. The biggest question about him is the fact that he's never been a coordinator. But I think he's such a good coach that it's ok.