It is one stop faster and that means more "bokeh" which people seem obsessed with these days. Both are great lenses. I have both and use both. Basically, if you want the fastest AF, you want to see less of the lens in the OVF, and you want WR, then you have one choice. However, if your fetish is bokeh and the mythical adjective "magic" ... others seem to think the 1.4 is the way to go. My opinion... you cannot go wrong with either.
oftheherd
Veteran
I never did controlled tests against other accepted good lenses, but did have opportunities to compare a fair amount of other photographers lenses (and photos) I traveled with or shared a darkroom with.
I was using Yashikor lenses except for a 50mm when I got my Fujica ST 901. I could just about never get flare with the Fujinon lenses, even when I wanted to for creative use of flare.
Evergreen States
Francine Pierre Saget (they/them)
The ƒ/2 has a little more bite at wide apertures, while the ƒ/1.4 has more of a soft/sharp balance. I don’t think the difference is substantial, though. The difference in depth of field at maximum aperture isn’t that visibly different either, because the distortion correction in software crops pictures from the ƒ/2 in closer to make it seem like a slightly longer lens. The barrel distortion on the ƒ/2 lens is pretty extreme if you turn off the correction in a RAW converter, but this is only a problem if you are stitching panoramas or you need lines to be perfectly straight (such as doing paid architectural work).
lxmike
M2 fan.
I love the 35mm 1.4, a lens that make my images better than any other