Upload & Sell: Off
Are you sure you like the IQ of film? So grainy…. And scanning is such a pain in the ass. I kind of liked my F4 but it took no more thought than any dSLR, just more money, and even with a Nikon 9000 I never got great scans because of film flatness issues and grain. And when I used a glass carrier I just got Newton's rings but IQ was better (you must use multi pass with Nikon scanners, btw, so it's slow and then spotting all the dust…I don't miss it much). Best case scenario 6x7 is as good as FX. That's what turned me off from it.
That said maybe I'm just jealous that you have the tenacity to keep with it and I didn't.
The RZ67 is a steal in general and that's a decent price, I think. That system is awesome. The 110mm f2.8, 65mm f4 and 50mm f4.5 ULD are truly fantastic lenses, even wide open. The difference between 135 and 6x7 is enormous, but not because 6x7 is so great (similar to FX, actually, but a little more resolution and a lot more grain), just because 135 is terrible by digital standards. The huge negatives are great.
But the system is HUGE. I brought it around with me and took some landscapes with it (that far surpass anything I've recently shot on digital because digital made me lazy and Velvia made me work for it) but it was always a big pain carrying that camera and those ridiculously large lenses around. The Hasselblad really isn't much better but it's smaller (until you put a wide on it). So would any 645 camera be much smaller. If you can handle the size and weight then it will serve you well but it's big enough to be an issue.
One other issue with 6x7 is mirror slap. Okay, the shutter is a leaf shutter so no problem, but the mirror slap is a big issue with sharpness and using MLU adds just another step to a reasonably long process… Only an issue for shots you need tack sharp (landscapes and product shots) so you'd have the time in these cases anyway. For handheld work (difficult on such a big camera, and you will tend toward low angles naturally because of the waist level finder) it's kind of trivial since there will be shake anyway. But there's more technique involved with 6x7 than 135. What the bigger negative gets you is better tonality and less grain, so depending on how big you print (or how much grain bugs you, some people like it on black and white) either 645 or 6x7 will be better. The rule applies with 1/(focal length) for shutter speed, so you need more light with 6x7 than with 135 or 645 not just for the generally slower lens speeds but also to retain the extra resolution that's theoretically available to you.
Whereas the F4 is a walk in the park and, like all modern SLRs, is basically a glorified point-and-shoot, shooting 6x7 takes a bit more practice. There's no meter in the camera so you have to be competent at metering (particularly when shooting slides) and then the bellows extension requires exposure compensation depending on focusing distance. The image in the finder is flipped horizontally, which I found actually resulted in better compositions (weird, right) but you need to get used to it. And because of the increased resolution you need to know your hyperfocals a bit better. Honestly, though, it's the most fun system I've used except for the size and it is pretty easy to use overall. My first shot was perfect technically when I moved from 135 to 6x7. Cannot say the same about my first photo on LF. Just make sure you have good meter (spot for landscapes, incident for studio) and some patience. I am selling mine soon but I loved this system; I would have preferred the Mamiya 7, admittedly, but the cost is outrageous. Digital has the same IQ as 6x7 (even APS-C is close) but is nowhere near as fun. I just got lazy and the cost caught up with me when I switched to LF.