Going from 1.3MP to 2MP or even 3MP generally does not create a really big 'wow'. That said, it depends on how wide the FoV is and what the buyer considers 'wow' worthy. The wider the FoV, the more likely it makes a material difference. The more a person cares about very fine details, the more they will be impressed.
The bigger benefit may be on low light and WDR. The TCM-3111 is a 3 years old camera, which means it has a sensor that is one or two generations old. Also, it does not have integrated IR. Consider a Hikvision camera with integrated IR and true WDR (here are 63 matches) or ACTi with the same (here are 15 matches).