Well, piie said it all in the proverbial nutshell. The ability to integrate with an AutoTrickler is the elephant in the room.
The EJ-54D2 looks like an interesting scale. Its improved precision is really nice. The ability to run off of four AA batteries might make it a good candidate for portable or in-the-field operation. And its USB interface would be really handy for weighing things like brass and bullets.
On the downside, its ergonomics - placing items on the platen from the top - looks a little sketchy. That would be fine for vertically-oriented objects like a piece of brass, or a flat-base bullet. Not so much for powder. It's also notably slower than the FX-120i. And I'm not sure it has the auto drift correction feature that the FX-120i has.
Lots of handloaders use the FX-120i, and so if you have any questions about that scale you're quite likely to get plenty of help. The biggest advantage of the FX-120i, by far, though, is its integration with the AutoTrickler. Even if you've convinced yourself that you're never going to go there, why close the door? I bet if you had a nickel for every handloader who initially thought that, and bought the scale, alone, only to later change his mind... you could buy yourself a pretty nice new rifle.
We're blessed with some really sophisticated tools in our world, these days. But the FX-120i / AutoTrickler combo is, for me, the closest thing to magic in the handloading world.
As always, YMMV. Whatever you choose, best of luck!