Both ranged empy are crazy good, actually. I fairly recently did Armageddon (which I preferred mainly due to use on two jobs that I play) and I love it. Does require some different thinking, and use of ranged crit sets with AM3 up - the white damage during AM3, with 50% triple damage rate on a ranged crit proc.... mmmmm, that's what makes the empys so good. My time with Arma actually made me kinda covet a Gandiva for physical focus with JR spam.
That being said, in comparing the empy options, Arma has more flexibility in that it's very good for all of TP, physical WS (Last Stand), and magical WS (Trueflight, Wildfire) - not to mention working for COR with the same flexibility. Gandiva is really going all in on physical /ra and JR, and if you're fighting something with strong physical resistance but susceptible to magic it will falter a bit. Still a damn fine bow though. JR is also a little quirky with the DEX mod, so requires some different gearing/augments for WS, but of course that applies to any bow.
For most people, I think Anni is probably less useful these days since enmity control isn't as big of a problem in the current game, and DPS is lower than empy/mythic/aeonic. True, there are situations where that isn't the case (master trial, as I understand, is highly focused on enmity control) - but those are fairly rare for most people doing standard endgame stuff with a competent tank.
Of course, looking at Verda's excellent contribution to the RNG community, you'll see that Gastra often has best performance of all the RMEA for RNG. It's just geared very differently to focus on Trueflight spam.
One last note, you don't really have to focus on Empy due to the VW campaign either. Can still farm HMP/cinder/dross and turn them into gil for whatever you want. I think the bigger benefit from campaigns is for people BUYING the materials, since a lot of bandwagon farmers will sell quick, so you'll see a temporary drop in prices and increase in availability.