I run a 203*, I have no issues hauling with it in the prairies here with light (under 12k) loads, even in the summer. I did however change it out for my trip through the mountains pulling 8k with a 185 or 190* T-stat. I'm glad I did because the EOT did climb to 225 a few times. It would have made me a bit uneasy if the 203* was in there.
I have to install a "weather front"/rad block off behind the grille in the winter even with my 203* or else if the outside air is below 50* the truck won't get above 190* EOT/ECT. With a 185/190* T-stat, it struggles to get above 155* in the winter. In the summer the ECT/EOT is usually always 200-210*. With the cooler temps starting here sometimes the oil does hover about 10-15* cooler than the coolant, but once on the highway or under load it slowly catches up. Mine runs cool, but runs better the warmer it gets no question.