I’m actually surprised to hear someone from my area. I also grew up in Detroit but now currently reside in Lansing. I can tell you one thing about the Ninja 250, there’s no way in hell a hybrid/fuel saver of a Honda or any other make that can go from Lansing to Detroit on 6 bucks. (Around 85 miles).
After I read more of the 600 articles it does seem to be a little chaotic. A lot of bikes have been suggested. The one thing that I have noticed in all my time of motorcycle research is that people focus too much on the cc number. People should actually look closer at the specs and see strokes and cylinders. For example, the Ninja 650 vs. Ninja ZX-6r. Like you pointed out the 650 has a parallel-twin but as for the ZX-6r runs on 4. 650cc vs. 600cc? Obvious who the winner is, no? Not to all.
My current research on bigger bikes is still in it’s early phases. I did note the Ninja 650r and the SV650s. I also was looking into see if I could get a older, 2001-2009, 600 4 cylinder and just remove some of the body. That way if I do drop it or something happens I really don’t have to worry about dropping 300-500 dollars on body work. Without some of the parts it’ll resemble a stunt bike. Once I get more experience I can then worry about the appearance of the bike.