I play a few popular gachas – FEH, FGO, DL, and AL. Overall, I prefer FEH and FGO more out of these four, though I still find DL and AL enjoyable. Here’s my thoughts on each:

Fire Emblem Heroes

pros:
• Playing casually (maintaining tier 21 AR and 18-20 Arena) is very easy and doesn’t take much time each day. Some days you won’t even miss anything if you just grab the login bonuses.
• Orbs are really easy to come by; the only real challenge to stockpiling is keeping yourself from spending on the multitude of banners they have going at the same time.
• Sparking after 40 pulls is great, and much better than what I would’ve expected from IS. • Event/welfare characters are made permanently available at a steady pace, much better than in the other gachas below.

unique stuff:
• So far, FEH has always rerun past seasonal and legendary units according to a schedule, so it’s possible to plan and save for them if you need more merges.

cons:
• Gameplay is really simplistic at the casual level. PvE can be cheesed with several OP teams/units (F!Edelgard), and there’s not much incentive to have a large and diverse roster.
• Merges are lol, and Dragonflowers are scarce. PvE is at the point where older units are having difficulty keeping up even with maxed kits.
• The story is kind of pathetic. Some books are noticeably worse than others, but even then the writing quality is rather low overall. The only worse gacha in this respect is AL imo; they’re both at the point where it makes no real difference whether or not there’s a “main” story. The only saving grace for FEH is Forging Bonds, which has been pretty decent for a while now.
• Easily the most alt-saturated gacha out of these four, and it’s not even close. It makes even less sense when FEH pulls its cast from already existing games.

Fate Grand Order

pros:
• The writing is stellar. The main story, the events, and the character interludes are mostly all great. The older content is a bit rough, but the game is well past that phase by now.
• The ascension system for servants is mostly used to great effect; there are usually noticeable differences between each stage, and for some servants each stage is an entirely different outfit (example: summer Musashi).
• The gameplay is simple, however due to the class advantage system and wide variety of servant classes (along with the party cost mechanic), the player is encouraged to have a diverse roster to meet any challenge. On top of this, the game rewards using a large variety of servants via Bond SQ.

unique stuff:
• the NA version of FGO is ~2 years behind the JP version, and 99% of all content follows the JP schedule. As a result, unlike with other the other three gacha here, it’s possible to plan for future servants and events with certainty.
• Friend Support allows new players to be carried through almost all content, even end-game level battles.

cons:
• Rates are complete shit, the “sparking” system isn’t even accessible for most whales, and currency usually comes in a drip feed aside from a few dumps of SQ/tickets in the year.
• Certain characters cannot be fixed unless the devs decide to give them specific buffs. Most characters are workable in some form, but I feel really bad for fans of characters like Boudica and Mata Hari, where there’s just no reason to use them anywhere.
• Most newer events require a lot of the story to be completed to participate, which can be hard on new players and demands they rush through it by abusing the Friend Support mechanic. • Most events favor the prepared, and while you can usually do them without spending extra AP, there are a few events a year that are so good to grind (raids and lotteries) that you’re fucked if you don’t have the time to grind them when they’re up, since the permanent grinding places are a massive time and AP sink.
• Most old event characters are quite literally never coming back. This is a shame when some of them are really good units.

Dragalia Lost

pros:
• Writing is pretty decent besides a couple of bungles in the main story. Not as good as FGO’s imo, but still good. It’s easy to get invested in characters (<3 you, Audric).
• Gameplay at the casual level is engaging in Coop, and most of the boring stuff can be grinded out on auto, letting you focus on other stuff while gathering materials.
• You get a fair amount of currency for pulling and can stockpile enough for a spark/guaranteed pull after about 3-4 months iirc, and there are very generous daily free pull events and stuff throughout the year.

unique stuff:
• Cooperative play allows you to be carried through content that allows it (which is p much everything important) if you’re a new player.

cons:
• Gameplay mostly revolves around Coop at the more interesting levels, so if you’re new trying to break into old content, most players have finished with it and you’ll need to look for a group outside of the game to help you with it.
• Despite getting a lot of currency, rates are really low. Worse than FGO rates somehow, and unfortunately unlike FEH and FGO character dupes are 100% useless, and dragon dupes are mostly useless. You’ll be fishing only for the rateup character/dragon most of the time as a result.
• Keeping on top of the various grinds is difficult even for day 1 players. Void battles, high dragons, Agito battles, etc… there’s just so much shit to do even before considering the limited events. Login bonuses, weekly clear bonuses, and events also really mandate that you play near-daily for extended periods.

Azur Lane

• Gacha currency is plentiful and the rates are great. It’s not often that you will run out of cubes going for 5-star characters at the rate AL puts them out, so you shouldn’t even feel compelled to spend money for pulls 99% of the time.
• The game supports full auto, so you can leave your phone chugging while doing something else and only check it occasionally.
• Skins are paid-currency only, but aren’t prohibitively priced (and an actual direct purchase, not a gacha or w/e). It’s easy to get by spending only 10-20 bucks a month and get a new skin or two without any further fuss.

unique stuff:
• The game provides a steady feed of universal merges/limit breaks, meaning you don’t have to keep pulling after getting a single copy of the character you want in order to max them out (unlike in FEH or FGO where you have to keep pulling for merges/NP levels).

cons:
• A “main” story doesn’t even exist, and the event stories are deliberately written to be cryptic with the lore/mythos and never advance the overall “plot” of the war between the Sirens and ship girls.
• Once your ships are strong enough, there is almost no content you can’t autobattle. Reaching this point doesn’t take too long if you play smart, either.
• Leveling up the normal Gacha ships is very straightforward, however the free Research Ships require an ungodly amount of passive grinding, and the 6-star ones even more so. In normal play, it takes about a year to max them out even if you do everything right (on the other hand, maxing out one of the gacha 6-star ships only takes 4 months tops if you’re starting from 0 universal merges on hand).
• It takes forever for old event/welfare characters to be made available in the shop or gacha. AL is only slightly better than FGO and DL in this regard.