I wanted to chime in on this. At home I have a small, efficient Honda to use as my daily driver, and the ProMaster available as needed. But traveling (and I plan to do quite a bit) its the ProMaster 24/7; cities, towns, freeways, backroads and parking spaces. So I got the 136" to make all these things a little easier, especially parking. Didn't really need more van or space.
Even though the 136" 1500 is SUPPOSED to have a different final drive (according to specs) and SHOULD get slightly better fuel economy (there's a whole thread about that here), it appears fuel economy is pretty much the same between the different sizes.
Pluses, minuses, pros & cons. You'll probably love whichever size you choose. If you're lucky you might find one painted Radiant Arctic Alabaster Frost.