I still say if the majority are Pre it is better (especially if they know how it works). A longer line of experienced travelers who do not have to take off shoes, remove laptops, or take out liquids, a group who is not setting off metal detectors nonstop, packing no-go items, etc, is a group that makes a line go faster anyway. Sure there will be some SSSS and some people who accidentally forgot the water bottle was full, etc., but overall, the Pre lines move faster anyway. My most frequent airports are ORD, DFW, and MCI. The latter has a single area for all security. Pre/CLEAR, and regular. It's still fast and easy.