Mamiya 6 is a great camera, which allows for fairly quick film changes - I have even done it while walking along (not tripped yet). A big Fuji GS690 or GSW690 (6x9) yield amazing results, but are huge and a bit slower to handle with film changes every 8 frames. I had reliabilty issues with the Bronica, so I do not feel that it is built to the same standards as a Mamiya or a Fuji, both of which are built like tanks. With any medium format system you stand out like the proverbial sore thumb. Leica may be smaller, but all are know to be expensive so theft may be a problem. The Nikon solution may be the best one - you will look like just anyone else with a Nikon, not worth bothering with.