I guess I will be the first to answer my own question.
I love the idea of the streetcar. I am a big fan of rail transit, and I would love to see streetcars return to Baltimore. I like the route. Although, it will run parallel to the light rail for a number of blocks, I don't think it is fair to say that the streetcar will duplicate light rail service. I see the streetcar as serving residents and tourists who live and are visiting, respectively, the Charles Street corridor. I don't think many people living in Station North or Mt. Vernon use the light rail to get around, but I do think they will widely use the streetcar. It is much for immediate, accessible and visible than the light rail. I'm also not convinced by any of the arguments that it will cause traffic nightmares or disrupt the character of the neighborhood. Charles Street has been reduced to one lane of traffic along at least some portion of it for the last few years and traffic has still flowed fairly well. Streetcars don't close down lanes of traffic, they flow with traffic. Also, with regards to the argument that it will ruin the historic character of the neighborhood, I don't see it. There are "historic" neighborhoods all across the world, or across Europe anyhow, in Barcelona, Lyon, Rome, Berlin, Prague, etc. that have streetcars. Why is Mt. Vernon any different?
That said, I am still concerned by the idea that the streetcar line will not be run by MTA or the city. I am also concerned by the fact that it has yet to be determined who will be primarily served by the streetcar. First, it was tourists. Then, it was Baltimore residents. Now, it seems ambiguous.
On to the circulator...
I really like the routes of the circulator. I think they cover a lot of ground and connect a number of critical neighborhoods. The Green Line, however, covers exactly the same route as the proposed Red Line (light rail line, not circulator line), and unlike the Charles Street Trolley with regards to the light rail, I think the circulator and the Red Line in this case will largely duplicate the same service. The circulator will be free, and because of its widespread service, I think it will be successful in drawing a number of patrons who wouldn't otherwise use transit. Nevertheless, the circulator is still a bus, and buses have rarely, perhaps never, proven to be as successful as rail lines. The circulator may be easier to implement, but I also think there is a greater probability that it won't work. There are already a number of shuttles operating in Baltimore that most people do not even know exist. If the circulator routes do get implemented, I would hope that the city would widely publicize them.
At first glance, I think the best thing to do would be to combine the two. Commence immediately one the construction of the Charles Street Trolley while at the same time implementing the circulator routes. In time, hopefully the Charles Street Trolley will replace on circulator route and the Red Line will replace another. Perhaps another trolley line could replace the third circulator route if it proves successful as well.