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I also enjoy the 20mm f/1.7 on my m43 system, as well as 35mm on a 5D. Can't really tell them apart all that much. The 20mm you see of micro fourthirds is 20mm on a 2xcrop system, but keep in mind that it's also a 4 x 3 aspect ratio. If you use 40mm on a 5D, it looks way different due to the 2 x 3 aspect ratio.
Regarding the question itself; ss there such a huge difference between 35mm and 40mm or 40mm and 45mm? I doubt many of these lenses are even EXACTLY their reported focal lengths. In other words, a 35mm prime can easily be 37mm without anyone caring, and a 40mm might be a 39mm.
Most lenses suffer from various degrees of focus breathing, which means they change focal length over the focus distance. I wouldn't really rule out anything based on a very specific focal length.