I have done mostly all landscape with my Mamiya RB67.. with its 90mm, that I got in February of this year, and love it, but need another lens. Now I am trying to differentiate what lens I want to purchase next, a 180, 250 or 360?
Looking in the archives, found that the 35mm equivalents for 180 is 87mm, and 250=118mm.
But what is the equivalent in 35mm for the 360?

The 180's are very available and inexpensive, but it seems that most who have the 180's, use them for portraits. I'm not really interested in portraits, but it sounds like that the 90, 180 and then 360 might be a good progression for landscape shooting. Since what I have read, seems to state that the difference between the 180 and 250 is very little, and should not be considered if one has a 180, for this aspect of shooting.

But what are your thoughts? A 90, 180, 360... or a 90, 250, ... or ... ??
thanks...

Background:
I shoot all three formats, and love my 35mm Nikon 80-200 zoom, and have never needed more than the 200 on the Nikon for what I was trying to capture. I also have a Cannon 35mm, with a fixed 400, that I have yet to get a descent landscape shot from, as its to 'zoom' for the landscapes I do, and to 'short' for wildlife. Birds ect.