Load Data from manufacturers > untuned QL data
QL is extremely useful for ballparking new load combos, seeing what changes affect pressure/velocity, but out of the box it's not going to be accurate enough to match ground truth. I often end up having to tweak H2O volume on the case, and burn rate / specific heat on the powder to tune QL to match the ground truth through testing. Once that's done it can make pretty accurate predictions and save you a LOT of time and money. But if you're looking at load data saying 29.5gr is max, but QL tells you it's not - trust the load data.