Thanks folks for the responses.....So the griddle most of the time will be used to make breakfast for 8 to 10 people....eggs, bacon hash browns, pancakes...I know with 28" I would not be able to do all of the them at the same time.....but perhaps not on the 36 either.....
Jeanie, seeing what you are capable of making, I can see how the 36" may not be enough sometimes.
Based on that I'd say 36" as well. Even then you will be doing multiple batches of food I think. I've only used mine once but I've realized that the food you cook on a griddle is less efficient from a space perspective than a grill. On a grill you can space the food pretty carefully. Lots of breakfast foods either spread out (eggs and pancakes) or at least need some working space (hash browns etc). The 36" space fills surprisingly quickly