If the 16" you refer to is the Bushtec, then my only problem is availability if you have a problem.
My trailer has 8" and covered many thousands of miles without issue. That said, I would prefer the 12" tires; less rotations per miles, and don't feel the small bumps as much.
Big advantage to the 12" trailer tire is availability almost anywhere in U.S. To me that's huge.
Whether it runs cooler is a moot point to me since these size tires are normally carrying a minimum of the weight they are designed for. If proper inflation is maintained I cannot see them running hot at all. My 8" covered 6300 miles in one trip last year loaded to the brim and stayed cool with no issues.