A marathon is not something you casually enter. The key is to find out your goal first. Most people have a time goal. This means running a flat or slightly downhill marathon. Most marathons are now geared towards time. Some even changed their course to make the course faster. The Edmonton marathon is a case in point. It used to meander through the valley but now stays on top to allow for faster times.
The next most important issue is the time of year. In my opinion, fall is the best time to run one. The weather is usually cooler and training in the summer despite the heat beats training in the dark and cold of winter. Unfortunately, if running for a Boston qualifier, the cutoff is too early now and you have to wait an extra year to do Boston for most fall marathons.
If not racing for time, the whole marathon experience matters more. Why train months and months to do a marathon with loops or large out and back sections? There are so many marathons, there is no reason to pick a boring marathon. We like running, but not that much! If you are racing for time and want an accurate course, why not just do a marathon on the track? Sarcast intended, but rumour is that such an event is being planned. We'll update this page when a track marathon is available!
Please see our marathon review table matrix for a comparison of one marathon versus others