Mini or full 4x5? I had a mini and it was "fun" kinda.... It just isn't all that great having to unfold out the bellows, composing, using the RF if it works, etc before taking a shot. With the Mamiya, the lens is there (no folding out or anything) and all you need to do is RF and cock the shutter. Done.
The 4x5 is like the mini only more obtuse. I'm thoroughly amazed that Press cameras such as those were used for so long and so succesfully, seeing as though the Mamiya or even the Graflex XL press cameras are sooo much easier to handhold and frankly aren't a breakthrough in camera technology.
Both will work. Both have great lenses, multiple backs, ect. Tough call.