The output from both systems is roughly equal, though the details are different. I can tell you that the Nikon 18-200 IMHO is a terrific lens for the price -- I have one installed semi-permanently on a D2x. Given your brief outline of what you intend to shoot -- which suggests you'll be on your feet quite a bit -- I would suggest that you put down the equipment you would be buying with each camera, and figure out weights and lens speeds that you need. Nikon will be lighter, faster and cheaper for equivalent FOVs. You can cover the full frame equivalent of roughly 18-300 with two very good Nikon lenses, of decent speed, or 18 to ~500 if you add a (very small) extender.
Canon's strength is in low light shooting where your back is against the wall and you have no options -- you're shooting very expensive, very fast lenses wide open at 1600 or 3200. For moderate priced lenses, Nikons are often a bit faster in the same length (because they're in fact shorter for the same FOV), so the available darkness factor levels out a bit, and you may be shooting a Nikon at 800 against a Canon at 1600.
I have been told by people who work with both systems that in terms of absolute resolution in good light with the same FOV, the FF Canons are slightly better, although the superiority is most often seen in test prints, rather than real-world shots.