I run platinum in mine, but some of the other trucks/equipment in the extended friends/family "fleet" run a mix of platinum and whatever is cheapest/at the pump. What we've noticed down here in the hot months, is that the platinum seems to "keep" better on equipment and trucks like mine that might sit for a few weeks without being used. I have no critical testing to back that up other than I don't feel the need to drain a def tank that's had platinum sitting in it for a few months in the dead heat of summer after having drained one that had platinum in it compared to the break down we've seen in cheap def that's sat in a tank unused. In the trucks/equipment that get run daily, we haven't really seen any issues running whatever API spec DEF that's cheapest to run since it doesn't sit in the tank for long.
Marion also has a youtube video documenting some of his compiled data regarding standard peak vs platinum, while it's not fully apples to apples data, it is encouraging. I'd like to see more data comparing the same truck doing unloaded hwy and loaded hwy driving, but some data is better than no data.
If I was running my truck daily I wouldn't use the platinum, but since it mostly sits unless I've got some long hwy driving to do or something heavy to move, I have no problem with the higher cost. Hasn't given me any issues when I need to hop in and do 500-600 miles in a week before it sits again. I also dose every tank of fuel and try to keep a battery maintainer on it when it's sitting.