Looking at the quick comparison above you can see how soft the X100F is when shot wide open, however, when you stop down to around F5.6 the difference is huge. The image sharpens up by a significant amount.
When compared to the 23mm on the XT-2, the first thing is the size difference. To some, the smaller lens may be an advantage, although, the ergonomics suffer greatly on the X100F. The manual focus ring is really tricky to use and the aperture ring always seems to be a little out of reach and awkward to find. In comparison, the 23mm lens is a joy to use with its much larger focus ring and an aperture ring that's always easy to find.
Holding the XT-2 is also much more pleasant with its better grip and button placement. I keep finding myself pressing the 'Q' button on the X100F which is a little frustrating not to mention the difficulty of holding it for long periods of time due to the lack of a proper grip.
I didn't test the focusing speeds extensively, however, in general, they didn't seem to be very different in performance. The XT-2 did seem a little snappier and nailed focus quicker and more easily. The X100F however, is no slouch and has been vastly improved when compared to the last model.
Also, the extra card slot on the XT-2 is extremely useful. Some may say it's not a big deal but whilst filming the video below, the SD card I was using in the X100F failed and it meant I lost all of the images that were taken on the day. It's not a huge issue for a camera like this but it's an issue nonetheless.