My second fastest was on a two loop course. My only issue was that the first lap was with the half marathon. When the half marathoners split off to go to the finish line, there was NO ONE around me. It was a solo run for 13 miles. That was harder than going through the same course a second time. But there were more people out cheering on runners the second half. So, it did not really seem that monotonous.
My cup of tea wrote:
I've done Erie which is a 2 loop race. I liked it for several reasons. As mentioned, my family was able to have more opportunity to catch me if they cared. I knew what lay ahead in the 2nd half of the race too.
Of the Erie race specifically, it's not too big or expensive or difficult to park/get to the start. And flat, flat, flat
I like some races with out and back features as well. I can see the faster runners that escape me from the start or figure out how far behind a target I am.
I've done Bay State once and it's a double loop. I actually found it pretty helpful in breaking up the race. I had family on the course and knew right where I would see them twice. It was one of my earlier marathons and I don't think I've done a double loop course since but would not be opposed. You could have someone with the fluids/nutrition that you want. I dunno I didn't find it boring in the race. It's also about how you approach it. My mindset wasn't I have to do another one of the same loops, I was thinking hey I get to see some cool people in just 5-6 miles (whatever it was) let's get to them.