Guy,
I have a Mamiya kit (as you know) with the 35mm, 45mm, 55mm, 80mm, 150mm, and 210mm. These are all the more modest, previous models in that none are the new "D" model (referring to the 80 and 150).
I tend to shoot wide stuff, but like the 150 perspective too. The 210 ULD is my newest lens, but I really like this one too. It's very sharp and seems to have a nice character to it. I've not used it much yet, but I did stitch four verticals to make a reasonably wide shot with it recently and it turned out very nice. I'm liking it now. (The same view with a single frame from a wider lens wasn't appropriate.)
The FoV of the 45 works well for me too. I've always liked 24mm on FF 35mm, so the Mamiya 35 fits there, but I have found myself using the 45 more often lately. Heck, like you I find the 55 good too.
We're lucky to have so many options, except my pack is a bit heavy! :ROTFL: