They are weakest piston design ever used in a 5.9, but they aren’t weak. Don’t run too much timing and you’ll be just fine. 60hp is nothing. They are designed around emissions and are easier to melt, and actually don’t burn as clean as the 03/04 style, but they work well for most users.
If you ever have to rebuild I’d go with the 03/04 piston style, but it’s not worth rebuilding just to swap pistons.