I have recently gone through the exercise that you are going through ... and it ain't easy. The one difference is that I had previously owned a Pentax 67, and a Pentax 645 and a Mamiya C330.
I ruled out going back to a Pentax 67 because I did want to be able to change films mid roll. I ruled out the Pentax 645 because I didn't want complicated metering (I use an assortment of handheld meters).
I seriously considered one of the Mamiya 645s but finally concluded that a square 6x6 format made more sense because I could crop 'down' to a rectangle; but if I had a 6x4.5 I couldn't crop 'up' to square. The Mamiya RB67 is a nice camera, but since I do landscapes, and trek about in the bush, I couldn't justify the weight.
I briefly considered a Hassie, but the cost of the glass is scary, and I don't buy the myth of European manufacturing superiority (Oh, I know I'm going to get flamed for that! To set the record straight: I didn't say it wasn't good equipment - whether Zeiss, Leica, BMW, Hassie, Rollie, Mercedes - just that I don't believe it superior to what the Japanese produce - Mamiya, Nikon, Bronica, Lexus, Infinity, Acura etc.)
I finally settled on a Bronica SQ-A with speed grip and plain prism (because I wanted mirror lock up, but don't need the flash capability of the SQ-Ai). With winter and Christmas, I haven't used it extensively, but what I've shot, I've liked. I've got a couple more lenses coming and hope to get out (weather be damned) and use it.
When it's all said and done, you need to sort out all the variables and determine what is the best fit for you.
Good luck in your search.
John