All these distinctions are meaningless. What Metrolinx needs to do to promote the idea of transforming the current GO corridors into rapid transit is an entirely new brand. When we say GO, there are a lot of people who just can't conceive of the idea of real rapid transit in these corridors. All they can imagine is running the bilevels a little more often. It needs a rebranding like Viva is to YRT buses. The concept would include 15 minute minimum frequencies at all times, electrified high-platform trains, relatively frequent stops, and seamless connection with other transit routes including buses and subways. It would extend out at least to the edge of the inner 905 and would provide a rapid transit backbone for the entire GTA. If someone wanted to go from Downtown Markham to Consumers Road, they would walk to the regional rail station, ride to Sheppard, then transfer to the TTC bus (or LRT) as seamlessly as you would from the subway today. The same would be the case for someone from the Lisgar area to Port Credit: they would ride their local bus to the regional rail station, transfer seamlessly to the regional train, then get off at Cooksville and transfer to the Hurontario bus (or LRT) down to Port Credit. The opportunities are endless and the cost is very reasonable. So much of the infrastructure is already in place.
The faster acceleration of electric trains will prevent the additional stops from adding much to travel time. For longer trips (Kitchener, Barrie, Hamilton), a higher level of service would exist with slightly more comfortable seating that would make fewer stops through the urban area. It would serve both longer trips and as a higher level express service within the city. All of these systems, of course, would be on the same zone fare system as local transit.