Get the 136, don’t listen to KOV on that stretch van!
No really it may depend on what you find.
We went 136 for a couple of reasons: Mostly to get into city centers like Boston, Key West, New Orleans, and St. Augustine all we have done in two years. We go to public events there including brew fests, baseball games, concerts, whatever. In these special cases the 136 is better. However you get 60 sq ftt instead of 72 sq ft inside. If you sleep across, have a galley, a place to sit to eat and a pottie you will use up most of the 136 real estate, our bed collapses to make this better but traveling we often leave it open like MsNomer does. If you need to sleep longitudinally or need a bath with real shower then you need the 159.
We ordered so we saved about $3000 by getting a 1500 and a 136. That pretty much paid for the diesel option we wanted. We would do a 136 again. I’d suggest this: Go out to your driveway and put down some of that blue tape. Make a rectangle 74" wide by 10 feet long that’s a 136. Then another 74” wide by 12 feet long that’s a 159. It will look much bigger. Now tape off a bed about 50” wide (ours is 54 MsNomer’s is 48?) then an 18” square for a pottie, a 22”X36” galley top, whatever else you want. It should be obvious. Remember you can sit in the seats outside that area by having swivels.
Don’t let indecision stop progress.