Got my JF 15400 today. Sorry, but it is not as comfortable as the TF. Wears heavier and more unbalanced although it is only 10.5mm (confirmed by me).
Alignment is not fully mastered yet in the JF. The numbers on the date wheel are not perfectly spaced. There are other small alignment issues in the hardware as well if you look carefully.
My bracelet screws I did not even touch until I ran the bracelet through some ultrasonic treatments: they unscrewed ok, but the tap is not perfect. Still very soft, deformable metal, so be careful and use the right head (1.2mm properly-sized screwdriver). It would be a shame to have a load of JF 15400s on the M2M with damaged bracelet screws.
Lume strips on markers are thinner than TF, and the bezel screws are better sized, no doubt.
I do not really like the tapisserie sizing, but the white dial is well done (black not as good, blue I do not know), and many will not really care about this, even if the dial does make this version kind of a fantasy 15400.
Crystal AR is very impressive, like many of the JF models. I am a 2XAR junky, but I do not feel glare interfering with my enjoyment of the watch and an immediate need to swap the crystal, like i did with TF.
CB engraving is very deep and crisp, and the deco plate is actually really well done, even though the whole idea of a deco plate (and not a full clone) is a little clownish.
In the end, I am happy to have both TF and JF versions. No need to really trade one for the other unless you want something the other one does not have. It is really an individual choice based on priorities.
Curious to see if the JF fatigues in daily use, as TF never led to fatigue, even on the SS bracelet. Like rnrprof said: If you have both, wear them for a full week before deciding which one to keep.