The Sea-Tac Marriott has given us good value over the years, which is worth much more than the "variety" of a new venue. Conference has had its annual meetings and banquets at venues all over the Seattle Area. That is because its the most central destination for out of town arrivals. Having had some of the rubber chicken served at the other locations, I'd say we would have to do very well in deed to do any better. You have to remember, there's more to it than just the banquet and the trophies. There are the meeting rooms and the hospitality suite and their costs to be considered. Besides that, I am always amazed to see the same staff year after year in what is a very transitory business. If they have good employee loyalty, they must be pretty good to deal with.
I think there is a cliche somewhere about not fixing what isn't broken