Actually, there is also regional bias and others factors. You will see that trains that have less number of stops are favored in NCR. That is why SG and SK are favored. Because it is easy to run such trains without bothering about stops as there are not many. PR and SS have home zone advantage. But then you will also see grand daddy Kalka Mail, which usually gets most favored among the daytime superfast gang consisting of NE, ANVT-HWH/Sampark Krantis/ANVT-BBS and some times Nandan Kanan, despite that Kalka Mail has way more stops. NCR is really messed up!