I used to have this problem. Its hard deciding which of these two lens i should get. Back when i got my Leica M9 i solved this problem by getting the 40mm 1.4. Its not 35mm but close. Now that i sold my M9 and left with an M8, this problem is back. M8 being not full frame, a 35mm will become something close to a 50mm, say 46mm?? Anyway, one problem i found with M8 is choosing the right focal length. All those RF lenses were design for full frame. 35mm is 35mm. I din wanna get the 40mm because it might be a bit on the longer side for the M8. I set my standard focal length as 35mm because this is how my X100S used to be and i'm comfortable with it. Then i should get the 28mm, it will be roughly about 35mm on the M8. But i wanted my lens to be small. all those 28mm with fast apertures are quite big. So to make things easy for me, i set myself to get a 35mm. but which one? a faster lens at 1.4 or a pancake but slower at 2.5. i'd love a faster lens as i like to play with bokeh and shooting in low light will allow for faster shutter speed. But based on reviews on the net, its a mix reaction but mostly said this 1.4 classic nokton has focus shift. and worst distortion and prone to flare. The 2.5 color skopar gets nice review, sharper, less distortion and less flare, able to get bokeh as well and cheaper too!
I knew in my heart that the 2.5 is a much better lens than the 1.4, but i just cant get f1.4 out of my head, i was placebo-ed by faster lens equals more bokeh, faster shutter speed. and i hate the fact that if i buy the 2.5, i might still buy the 1.4 in the future just for the sake of the 1.4.
Sigh. Story of my life!