I have both the Bronica RF645 and the Fuji GA645. I enjoy them in different ways. Both have given me excellent photos, and both lenses are just spectacular. The Fuji is a perfect travel camera, with a very good meter, and no thinking auto everything. You just concentrate on composition, which is the most important aspect of photography IMO. You can use it in manual mode, but it's difficult, as you need an extra hand and extra fingers to push the right buttons.
I use the Bronica when I want to have control over the whole process of taking photos, from the focusing, to the exposure selection. The camera controls are a joy to use, butter smooth, and it gives me a lot of tactile satisfaction. As a mechanical engineer, I truly appreciate how well the camera works. But..it has given me a lot of trouble. Right after I bought it used on eBay, the flexible control board fried and I had to send it to Tamron in Japan to get it fixed, as no one would touch it here in US. Expensive to get it done. Last year the advance lever, a know problem with the RF645, stopped working. Walter's Camera Repairs in LA was able to tackle the job at very steep price, and now I have a working camera again. I justify all the trouble I went trough with it by the satisfaction of the result I get from it. If I had to do it all over again, I would probably go with the Fuji and spare myself a lot of headaches.