We've towed our 2007 Acadia across the country and back, more than 20k miles altogether. Both the Yukon and the Acadia are excellent vehicles, docile toads and have similar interior space, so it's pretty much a matter of what you prefer in terms of styling.
The Diplomat won't notice the weight difference except on long, steep grades where there is an extra 1000# to get the Yukon to the top of the hill. And probably not much difference then either.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL