Regardless of the race, you still have to traverse the 26.2 miles, but selecting a marathon tailored to your preferences will enhance your experience. Which of these factors are important to you?
Degree of Difficulty: Are you trying to run a fast time? If so, look for a flat marathon. If you go on a marathon’s web site, there will be an elevation chart. You also might want to consider the weather. Though you never can be sure what the weather might bring, you can look up the weather history from previous race days to get an idea. It’s hard to run a fast time in hot weather or in windy/stormy conditions. If the marathon itself isn’t enough of a challenge, there are races that pride themselves on being the toughest challenges out there.
Scenery: Do you rely on breathtaking views to get you through the 26.2 miles? If so, there are many races that promote themselves as the most scenic marathons. These often can double as a great getaway marathon for vacations.
Size/Convenience/Cost: Big city marathons are exciting because they have the feel of a 20,000 person street party with cheering spectators lined up practically the entire route. Other benefits are that you will almost certainly have a pack to run with, the finisher medals are high quality, and the SWAG (giveaways) is better. However, the cost is about twice as much (about $200 for the big city vs. $100 for the small marathons), and some big marathons require a qualifying time or have a lottery system. The logistics of the big marathons are also less convenient. You often have to arrive way before race time because parking is far from the start line. In addition, it often takes several minutes just to cross the starting line and once you do, the course is often so conjested that you can’t begin to run your desired pace for a couple miles.
Entertainment: Some marathons provide entertainment along the course and/or after in the form of post race parties, beer gardens, or musical performances. Again, the race’s web site will highlight these features.
My advice: Decide on an approximate date to run your marathon, look at an online race calendar to see what races are held during that time, and browse several marathons’ web sites to see which one best suits your needs. Just be sure to plan ahead because all marathons have an entry limit and some fill up fast. You don’t want to be left out.