I ran Dopey. So first the expo is your standard runDisney expo.
The 5K is a fun run, so unless you're running Dopey, don't expect an official time. It's probably the best course of the bunch because it's mainly in Epcot. And remember when I say fun run...don't expect a PR. The 10K was my first of the distance so I'm not a great judge on this one. These start lines are right next to the runner's area.
The half marathon was a good course. You spend a little bit in the parks but mostly running to and from. What threw me through a loop was the unexpected 1+mile walk from bag drop to my starting corral. And once you're in there say goodbye to the porta pots (although there are plenty before you get in). The course seemed to go by pretty fast.
The marathon seemed to be the busiest event. And although it wasn't my best race. I still enjoyed it. There is plenty of entertainment even though sometimes you're lacking "scenery." Lots of support too. Hollywood studios was my favorite park to run through!
I didn't think there was any aspect of the course that was too crowded.
If you plan on running Dopey, if you want a "finisher's photo" with all of your medals, you'll have to carry them with you since bag drop is after you leave the finishing area. I saw plenty of people do this!
I rode the buses from the resorts. It was a quick ride for the most part. But sometimes a wait after the race. Some runners when right to the parks after finishing (I did not).
Since it was a colder race weekend, I'm happy my parents did chEAR squad, since it was in a "climate controlled" tent and had food!