kin2son

Neither.
23 is too big and bulky, whereas 27 is too slow and narrow.
X100T is not bad (I own one), but it's overpriced imo, no articulating screen and way too soft and hazy at macro range.
Therefore your best bet is 18 - small size, relatively cheap, has an aperture ring unlike the 27, and wider than 23 (just crop a lil if required).
In fact that's exactly why I bought mine.

Between my X-T1 and my girlfriends A7, I always found the skin tones from Sony more warm, but the white balance also more on the "yellow" side. As for sharpness, I agree with addicted2light - Fuji RAW needs quite an mount of sharpening (JPG is very crisp), Sony is sharp already. 

So are you saying the 27 is that much better than the kit zoom @ 27mm?  
 
Same applies to 27mm? 
That's the whole point isn't it? 
Street lens is about being small, light and unobtrusive. Most importantly it's about the focal length.
 
Kit zoom totally defeats the purpose.

I personally think it is for streets.

IQ should never ever be your first priority of choosing a lens for your usage, focal length is.

I just can't agree with choosing 27mm simply because it's slightly better optically which tbh can only be spotted when pixel peeping.

Size and weight is a wash, and I much prefer having the aperture ring on the lens like my other X lens.

28mm is a very very popular focal length for street shots, just look at Ricoh GR and the new Leica Q. 40mm isn't wide nor versatile enough to truly capture the essence of streets imho.
 
I took my GR to Japan last year, and now that I shoot with Fuji the 18mm replaces it.
 
Here are a few examples -
 




 
The close focusing ability of the 18mm is perfect for food shot as well which the 27mm can only dream of
 

^^ not sure if this helps, but I personally use the front custom button to change focus mode...

^^ not sure if this helps, but I personally use the front custom button to change focus mode...