@lolix You're right that AW Sherry is probably the single biggest overall improvement to his team that one AW would make but that doesn't necessarily make it his best choice if it isn't enabling new maps. It's probably still just Spica IMO for higher Crystal Keeper difficulties, which means more DC which means faster future AW to improve his massive potential team. As I said though, if the opportunity comes to AW a unit and you think you have a better choice to enable another map then go for it. We are kind of splitting hairs at this point, but the game is a massive grind that could always be skipped with enough SC, so building towards a team that can farm more efficient options should always be the goal when deciding what to level first if progression is your primary motivation.

The easiest way for OP to answer his own question honestly (and this will work for any person with these sorts of "advice on what to level next") is to look at a guide for the next map you can't yet complete and figure out what you need to level to get there while taking into account any premium units you may or may not have available. Obviously you'd put more weight on beating the best story map option and higher thursday and monday daily options if possible since those tend to be your limiting factors. Event maps can supersede everything in the short term depending on what level of unit you're gunning for.

@Nero AW for higher stats is definitely nice, but don't be fooled, the passives and abilities are almost always the reason for deciding what to AW next. You just don't get enough for it to be worth it usually without some sort of percent boost to teammates or practical ability.

As an example, Spica's damage at 50cc70 100% aff is 502 and at AW99 is 589. To realize that 17% boost means leveling her from 1 to 50 again and throwing 11 plat armors and 33 plat spirits which could level multiple other units. It's even less if you don't go for max obviously. Compared to 20% extra dmg against flyers and 7% to ALL archers attack with no extra investment past the AW itself. Until we get harder maps, you just don't need that many stats per unit slot gained from levelling AW units.

To provide an exception, my next AW is going to be Bashira over multiple other "better" options (Lilia, Zola, Mehlis, Iris off the top of my head) even though her Priority Ranged ability is nearly useless. That's because a second AW archer will let me farm Crystal Keeper G over X since I already have the Artillery Officers levelled to handle the end rush. It will take me an average of 48 runs of G over X before I "earn back" the 100 DC I used on the AW and start turning a profit, which is about 3 months at 4 runs a day (saving up and running right after and before resets makes 4 runs a day possible, and even 5 runs at higher prince levels). This also doesn't even factor in the increased Charimsa cost either, which means a little less fodder acquisition during no event weeks, but I also get a bonus SC earlier for map completion. I've decided as small a bonus as that is that it's worth doing because I don't think delaying AW my more core units like Iris by 100 crystals will affect my ability to complete event maps in the meantime. Things could change if the event climate heats up but this is my perspective after 4-5 months of play. Most people wouldn't think about this or even care at all, but this is how I analyze things to get the most value out of my limited resources.

This turned into a wall of text but I hope my formatting was decent and everyone that stuck through managed to glean a bit of information from it.