The Speed Graphic plus tripod will be such an encumbrance on the streets of Manhattan, especially your first time there as a tourist, that I'd avoid that option and go with the RZ. Especially since the SG will limit the number of shots you can take and you'll always be second-guessing yourself as to whether you should take a given shot or not. And then you'll take one, walk around the corner, and find a much better shot waiting to happen that you CAN'T take because you're out of film, or you know you need to save film for other shots you want to get, etc etc. Although frankly I'd rather have my Rolleiflex than an RZ for street shooting (much stealthier, lighter and easier to carry, 12 shots vs. 10).