Regardless whether you buy the original Gloomhaven, the even bigger Frosthaven, or the much more affordable Jaws of the Lion, the core game is always the same. There is a scenario with a hex-based map, and it is usually a few rooms big. Gloomhaven scenarios tend to have roughly the same size, for the simple reason that the length of one scenario in turns is limited by the rules of the game. You start with a hand full of cards, let's say 9 for the Demolitionist in Jaws of the Lion. You play exactly 2 cards per turn, so after 4 turns you don't have enough cards anymore to play another turn. So, you need to take "a rest", in the process of which one card gets removed from the game, leaving you with 8. Then you can play another 4 turns, another rest, leaving you with 7 cards, and only 3 turns for the next cycle. Overall you can't play more than 4+4+3+3+2+2+1+1 or 20 turns. And there are other methods of removing cards from the game, which in consequence shorten this even further.

So all Gloomhaven scenarios are designed to be finished in under 20 turns, which given the speed of the characters and the time needed to kill enemies results in dungeons of a certain size. At level 1, the Demolitionist has 9 level 1 cards, and three "X" cards to choose from. But he can only ever take 9 cards into a scenario. With just 3 extra cards, at least two thirds of the deck will be identical from one scenario to the next. Some cards are simply better than others, while other cards only fit into a specific build. Over the course of the campaign, each character only gets one new card per level, and it can take several scenarios to gain a level. In summary, you are going to play a lot of scenarios with a similar size, using a similar deck of cards. And while some good work has been done to try to make the scenarios different from each other, with different objectives, and the occasional added difficulty of a boss mob, in the end the basic structure of the cards necessitates a somewhat similar gameplay. Overall, Gloomhaven plays like a puzzle game, like Candy Crush: You play through different levels, but the basic puzzle remains the same, and you are trying to "git gud" to be able to handle all the small variations of the different levels you play through.

Agemonia is a very different game, although it at first looks a bit like Jaws of the Lion: Scenarios printed as pages of a book, and miniatures engaging in tactical combat against monsters represented as standees (unless you bought the miniature expansion). But the basic structure of combat is a lot simpler, based on rolling dice. Instead the main feature of the scenarios and the game is that all over the map there are printed letters, with a range information. When you get in the specified range, you draw the story card with the corresponding letter. And the story card makes something happen: It gives you some information, it might pose a challenge to be solved with a skill check, or it might spawn some monsters.

As scenarios in Agemonia tend to have "fail forward" mechanics, where you don't replay scenarios for failing, the normal situation for an Agemonia scenario is that you are playing it blind. You simply don't know what will happen. You could concentrate on the main mission and avoid uncovering the story points that are a bit off the main path. But of course those story points might be interesting, or give a nice reward, and usually there is a end-of-scenario award for having uncovered all of them. Then again, there is often some sort of timer, which pushes you to not dawdle around forever. And you rarely have advance information about what will happen; it could well require a skill check in just the stat that your character is bad at, require an item another character is carrying, or result in you being attacked by monsters.

Overall, Agemonia is not a game you "git gud" at so much, but rather an adventure game, a game to be experienced. The joy is playing together, and getting into all sorts of situations together. With advance knowledge of all the story cards of a scenario, you could optimize it as a puzzle, but you are practically never supposed to have all that knowledge. You'll try to get through all those situations as good as you can, but there is luck involved, which gives everybody a good excuse if things don't go as planned. And it isn't all that bad if you don't get the best outcome of a scenario, you can still play on perfectly fine. It is a lot less serious than Gloomhaven, where playing badly and failing the scenario will get you some nasty looks from your fellow players, as now you'll have to play it all over again.

As a roleplayer, I enjoy Agemonia more than I enjoy Gloomhaven. There is more of a sense of adventure in Agemonia, exploration and discovery are an important part of the game. Experiencing a good story is more important than playing optimally. I also enjoy character development more in Agemonia, as you start out with just 2 different actions you can do during your turn, and end with 8 different actions, with each character over the course of leveling having 17 different options from which to build those sets of 8 actions. I find the story of Agemonia less thin than that of Gloomhaven, which might have to do with there being some story during each scenario, not just a prologue and an epilogue. But of course, I can see that gamers with a different character than mine might prefer the more hardcore Gloomhaven over Agemonia.