There is not a huge amount of difference between Attack on Titan Manga and Anime except being one is in Anime form and other is in Manga form.
Major difference that we see in the series is that anime shows 104 Cadets training later on in the storyline as compared to manga. In the manga we can see Tross is shown breached before getting training for a very long moment.
Another difference that we observe in the anime is about Annie how she laughs after confronted about being a women. Isayame in the manga put her laughing but after he regretted to not put it in the anime. After regretting he requested to back Annie laughing in the anime.
There is another difference like Annie beating Eren in the fight. So, while both are fighting instead of defeating Eren, Annie slowly analyzes Eren and ends the fight. To the their fight, Mikasa comes out for help between them.
We get to see Annie crystallises only after being taken out by Survey Corp. But in the anime it was opposite as in the anime Annie crystallises during the fight with Eren.
Their is also a big difference about the name of the weapon that they use, in the manga the weapon is known as Veritcal Manouvering Gear instead in the anime it is called Optical mobility gear. So, we can see a lot of minor details that are changed in the anime. This was also die to the reason that anime producers were forced to not use the name mentioned in the manga but to use a different name. But, still the weapon is cool in the end whatever it may be called.
In the manga where Sasha don't have particularly a major role but in the anime she is given a big role, this is due to the reason of her popularity which increased in the anime and hence the producers give Sasha a bigger role in the anime.
There are also a few subtle differences which we notice in the anime like different lines or word style and also different art style which is used in the anime. So, there are quite a few differences but not something that makes a big change.
Did MAPPA Studio didn't do a good job on Attack on Titan season 4?
It first came as a shock to every Attack On Titan viewers when there was a announcement that Attack on Titan producers are going to change studios. Changing studios is actually a big deal as it can change the whole vibe of the series which was perfect till now.
It was also due to the fact that studio WIT set the bar so high for the series as there was nothing bad in the animation quality or art wise. It was also thought that any other studio would not be able to match up with art standard of Wit studios which was already set so high.
It was a little bit on the downside when Mappa released the first five episodes. In the episodes the art style of Beast Titan looked a bit funny. It didn't have the same kind of detail as Wit used to have on their hand drawn beast honestly saying.
Keeping these thing aside the characters, voice acting and the CGI of this series have been so well done that these minor details can be left aside. To be honestly saying animation quality of Mappa studios is lit. But it just didn't ends here Mappa put a lot of effort after the first five episodes and we can definitely see that after Sixth episode.
When I firstly saw episode 6 it was just awesome, it hits differently. If we see the previous work done on the Attack on Titan anime it just went to whole another level. In this mew design Levi and Mikasa looks even more cool than before. So, we can say that it even surpasses Wit studios work.
This time studio is trying to focus more on manga type art style or staying true to the manga. Which they accomplish very well. So, at the end Mappa studio did a great job for Attack on Titan Manga.
Do you agree that Attack on Titan is one of the most overrated anime/manga of all time?
Well, to some extent we can say that this is correct because as we can see on the Imdb rating of the anime it is rated quite high this is due to the fact that fans of Attack on Titan rate every episode of the series 10/10 even if there is some flaw in the episode.
So, honestly saying there are no true critic of Attack On Titan Anime as we can only see hardcore fans of the series as their only goal seems to push the rating as high as possible. And on the other hand haters just want to downvote it.
So, rating only doesn't make it better anime as it only push the rating up and there is no difference between rating of the anime and the content of the anime.
There are lot of things to consider to if to make it a good anime for example music, artwork, directing etc.
But the thing is it is a good show and it is overhyped as from the characters point of view they are pretty simple like any other anime character we can see like a main character who doesn't give up in any kind if situation, the friend he is having is utterly useless and is only present their for character support.
So, this was the issue with characters but the storyline too is somewhat underwhelming as it is only about fighting and more fighting. Attack on Titan definitely have some flaws in it. So, it is overrated manga/anime series.