That depends on your location and your RF environment but one thing I did notice was that, there was a different filter for site Zone 1 and site Zone 2. You don't see that too often in the same system but it happens.
Sample on global filters first watching your RSSI, noise level and error rate. When you find the best filter for both sites return Global to normal which is default and drill down to site options and apply the best filter to each site. Don't worry about the sites in the subway system unless of course you are in the subway system. It may be different for you but I found one site was invert and the other site was wide invert. What works for you won't necessarily work for me as its dependent on your RF environment. People will say the RSSI doesn't matter but I use it anyway. You can use your ear too. LOL
PS make sure to put the filter indicator on your display oh, it makes it easier.