I had a Mamiya RZ and for handheld work it was not good. After an hour I got a little hand shake (actually a lot, I hate to admit). So that meant it needed to go on the tripod. Not what you are probably looking for. The Hasselblad is much more manageable in that regard and I like shooting it handheld. The Mamiya 645 Pro was also nice handheld, but I just found the square format worked better for me between the two.
I haven't used either of the systems you've mentioned, but look at their weight and bulk to help you decide. That to me is much more important than whether the camera takes batteries. Spare batteries are cheap, so carry a couple in your bad at all times.
The other thing I find with MF SLRs is the mirror slap really makes me flinch, so I find I don't get as sharp of images handheld as i could. I've tested this with mirror lockup and a tripod and I'm pretty sure it's the mirror making me move, not it vibrating the camera. In this regard a range finder is very nice. I love the Mamiya 7 and the Ansco Super Issolette (which may be in your price range) for this reason. So try the camera before you buy. Maybe consider a pair of fuji range finders, I hear they are excellent, and have different focal lengths available.