If I'm not mistaken, 1.7 and 1.8 will be a bigger difference than 3.5 and 3.7 due to the non-linear way apertures work.

For example, from f2 to f1.7 is half a stop. From f4 to f3.3 is half a stop also. 0.3 difference, vs a 0.6 difference! Look at this chart:

https://photos.smugmug.com/photos/i-FbncDFX/0/O/i-FbncDFX.png

So following that thinking, even though 3.7 - 3.3 = 0.4 and that is greater than 1.8-1.7=0.1, the 1.7/1.8 difference will still be greater than the 3.3/3.7 ratio.

Aperture differences are not a 1 to 1 ratio. You have a circle, and you increase the diameter of it by a small amount, the circumference will increase. An aperture of 3.7 is smaller than 1.8. meaning the 1.8 alerture creates a larger circumference. If you make it bigger even by a small amount (lowering fstop to 1.7), the circumference gets much larger, comparatively to a 3.7 opening up to a 3.3.

I'm not great at explaining this and i dont fully understand the math myself. But i hope this helps.

Maybe someone who knows more than me (i know very little), can either correct me, or explain it better.