If you already shoot other formats (such as 35mm, then what focal lengths work there for you?
i stopped working on 35, but had a 24-90. But i do not want to have a rocket lancher in by bag when i go into the mountains... Wide angle is often nice for holiday pictures, not for real images. And if I need real wide, than I use my 4x5 and put the 6x12 back onto it. For the "Fast" work i want to use the 6x6.
For me the wide angle would be a lens to take along when shooting pictures when we go out with our photoclub, or on holiday (landscapes,mountains).
The 40 is nice, but a beast and not affordable. for architecture i use a 4x5.
In that case Willie I would go for the 50mm, it has angle of view of 75 degrees (about the same as 28mm on 35mm) that I think would be the most useful for your purposes regardless of the relative cost of the lenses , if you already have the 80mm standard lens, to me this would be the best buy.