I recently acquired a Makina 67. I've found that I take it along much more frequently than my Pentax 645 system, despite the rather beautiful lenses I have for the latter camera. It's very portable, and yet 6x7, with a very capable (Nikkor) lens.
So purpose and opportunity are factors. I just need to find a protective case, too, so I will bring it along even more frequently (I cannot always bring the bag along).
That said, the Pentax 645 system has incredibly sharp lenses and the upgrade path to the 645D. Very happy to have both. The 120mm Macro lens is stunning. So is the 35mm. Or the FA 150mm, FA 200mm.
I considered the Mamiya 6 for a portable system, too, but have no experience with it. I would be interested to hear about its rendering.
These days, with eBay and forums, it's not too costly to try out a used system. So go with your intuition.