The X100 line of course has a 23mm lens, which is the equivalent to a 35mm lens on full frame. I would prefer a X100 over a 23mm lens, due to the new possibilities of this combo and due to having a 35mm equiv ready at all times, but of course its also more to carry. The new XF10 should be mentioned as well.
The reason one might upgrade from the X-E2 is the relatively slow autofocus, compared to more current generations.
Thanks for that, I looked into the XF10 but the lack of viewfinder and the extra stop missing does bother me a little bit. I am glad you mentioned the autofocus, but now that I think about it other than the slow autofocus I am quite content with the X-E2.
If the options are strictly x100f or 23mm for your x-e2, I would get the x100f. If you're looking for other suggestions, I would trade in the xe2 and pick up a used xt2. They are priced very sweet right now and you could still have some left over for another lens. You have wide angle through 55mm covered. You need something long. I like the Fuji 50-230. It's lightweight, cheap and sharp and takes nice portraits at the long end. Great for outdoor shooting, not great in low light but so affordable. Or a used 90mm f/2 - a great portrait lens. Definitely look into used/refurbished to stretch your dollars. Your avatar doesn't say where you live but if you are in the US, check out Fuji USA Buy/Swap/Sell Facebook group. Lots of good deals there direct with other photographers so cutting out the middle man.
I would want to trade in my XE2, but it has scratches all over the body so I don't think I would be able to sell it for a high enough price to justify the sell. I was also thinking of 90mm or 50mm as well, as the 18-55 is pretty weak in a low light condition. And thanks for recommending the FB group! I just joined.
I would get a X100F. Reasons...
Leaf shutter, excellent for flash photography.
Optional Tele Conversion Lens TCL-X100II. Turns your 23 to 50
Another vote for an X100F or X100T if you can find a new one. It's a great all-rounder. The hybrid viewfinder is killer, too. If you get one, the TCL-X100 conversion lens is identical to the newer II model with the exception of a magnet that automatically tells the body it's there; otherwise it's a quick toggle on the menu with the older version. No image compromise I've been able to see. The X100 series is an excellent street camera and as big as I care to use for that kind of shooting. The little Ricoh GR/GR II is another possible option for street.
X100T sounds like a good option too. Seems like used ones go for about $700?