I think safest would be to use hardware cloth for everything.
But, since we are not made of money.... You could use whatever is cheapest to bury under ground to deter predators. Then, anywhere where the ducks might be sitting use hardware cloth. You could use something a bit cheaper for the rest of the run, especially the top, unless you have a tree right up against the run which would mean that more predators are more likely to be running around on top.
I think many people use hardware cloth for the bottom 1 to 3 feet and then use a less expensive wire for the rest of the run if the animals are locked up every night. If you are not going to lock them up every night, then it is best to use hardware cloth on the entire run.
Also remember, besides the raccoons reaching in with their hands, and the raccoons unlocking everything, the other big problem is that dogs can be very strong and will grab chicken wire or welded wire and yank it apart with their teeth.
I know, major pain, and lots of money. Just remember that doing it all right the first time means it will last for years and save you lots of heart ache.