Gunner Main/Ranger Sub Question

So if I main Gunner and sub Ranger, should I pick Stationary Fire or Mobile Fire? Some of the PAs make you move, but I don't know if that actually influences the ability or not.

Prefacing this with a "Ranger is not that great of a subclass for Gunner despite them both being Ranged classes due to Ranger's multipliers not being conducive to TMG gameplay in most cases."

With that out of the way, Stationary Fire only takes into account whether or not you have been stationary (ie. no changes in your X, Y, or Z position) for at least one second at the moment you activate the PA. For a PA that moves you during it, if you were stationary for one second when you hit the PA button, Stationary Fire will be active the entire length of the PA even as you move, but it will not be active once it is over until you are stationary for a second again. With TMGs this can be harder to set up since they have a higher reliance on comboing PAs and moving in melee range compared to Rifle.

On the flip side, Mobile Fire activates in the situations where Stationary Fire does not. Basically, as long as you have not been standing still for at least a second, Mobile Fire will activate. This is the one that is most conducive to TMG gameplay since you are more likely to be in a moving state when using them.

To expand a bit on AndrlCh's post, having mained both Ranger and Gunner at different points, the "one full second of being immobile" requirement on Stationary Fire is really only practical for Launchers, which are exclusive to the Ranger class unless you find a multi-equip variant like the Sigma Bastad, as the Launcher weapon type more or less commits you to a stationary position whether you like it or not. For TMGs, Rifles, and even the Gunblade (the poor, unloved step-child of every class) though you want to stay mobile, re-positioning fairly often unless you plan on hanging back and "sniping," which is really only practical for Rifles, for which you might as well main Ranger and pick a better subclass like Hunter or even Summoner as Gunner doesn't really have any skills that specifically benefit Rifles.

So, yea, long story short Mobile Fire is the better bet, but overall as AndrlCh said there are better options for subclass that aren't so conditional and offer more overall benefit. Regardless of which one is main and which is sub Ranger and Gunner just don't have much synergy. As little sense as that makes in concept.