This is true, but only to an extent. Of course every rider (discluding railfanners) will ride the first train they see. As for the instances in which you see passengers purposely avoiding one train just to ride another, I'm willing to bet that occurs only when special circumstances such as stench, rowdy passengers, skip stop service, poor A/C, ect. occurs.
However, you must be downright stupid to not prefer an NTT or a 75 footer over a 60ft SMEE generation train. There is simply no reason as to why a person wouldn't prefer to see an NTT. If one comes by, then its a bonus. If a SMEE pulls up, oh well. However, you must acknowledge the fact that people prefer NEW things. It is the extent to which we are willing to give up commuter time which is in question, and in the majority of cases, the answer is NO, but to blantly say that people don't care at all if an NTT pulls up is false though.