I'm sure it would look more balanced on an X-Pro1, but yeah, that's definitely quite a bit larger than the 35mm. The X100S will still win for portability despite whatever advantages the 23mm f1.4 ends up offering
Seems like the most obvious cross system comparison would be to the Sony Zeiss E Mount 24mm f1.8, which is a little smaller but similarly (right now on special) priced. However, for the same speed, I wonder how it will compare to the Sigma 35mm F1.4 available on several mirrored system which is bigger but comparably priced also.
It's bigger than the 14mm.
Here is a link to the official Fuji page with some sample images.
FUJINON LENS XF23mmF1.4 R | Sample Images | Fujifilm Global