TLDR : The manga kinda lost itself and became a simple shonen instead of a parody of shonen. Some fights are drawn out and dont feel like much is happening. The pacing is slower and events are overall drawn out, this gives less impactful and emotional scenes. Some informations are very unsubtle, it almost gives us no room for thinking and interpretation, which gives us a story with less depth unfortunatly. It just became a simple shonen for casual anime fans (not necessarily bad but quite far from its origins).
/!\ SPOILERS /!\ (review not finished, might update it)
However, we are talking about the manga and compared to his counterpart, he leaves a lot to be desired. This will mainly be talking about the Monster Association Arc, since it has taken such a long time to develop it (atleast in the manga). We have to aknowledge first that they are a lot of differences between the 2. The first is that there is a lot of added content, and I mean a lot. The martial art tournament is one example, and a good example of almost useless new arc and borderline boring. Since this tournament have a lot of new characters, it is quite uninteresting to watch because we already know that saitama wont loose and because the new characters are only briefly introduced, we don't really care for them nor root for one. This gives us a dried out tournament with almost not interest to give in. Furthermore, it almost is totally useless, only used to have an excuse for saitama to be busy while the monsters are rampaging and to introduce a certain character.
One problem that I already said is a lot of new content (not necessarily bad), but a lot of it is useless/doesn't bring anything to the table, such as the many variations of monster Centipede, the elongated battle of Psycho vs Tatsumaki, the lot of meaningless drawn out battles, ... This impacts a lot the impression of the fights left on us. The pacing feel slow, fights drawn out, which could be interpreted as a parody of the shonen genre, but even though the pacing is slower, you still dont feel that much is happening. The new added content doesn't feel like it helps necessarily the plot, sometimes even acting against it. Garou in the webcomic seems cold hearted, concise but overall he doesn't necessarily seem like he could be a good guy in the inside. After the fight, Saitama is the one making us realise how actually Garou isn't as much evil as we were lead to think at first. However, in the manga, there isn't a lot to think about. Since the start, Garou doesn't feel like much of an evil guy, much of a monster. He feels as just an asshole,the manga is very on point since the start on what Garou is. It doesn't leave much to think about.
With the art improvement, comes the failure of the jokes. A lot of the jokes fall way more flat to me personally at least than in the webcomic. This leads to point out that the webcomic which I could easily categorize as a parody of shonen. For the manga, I couldn't categorize as easily as a parody. It feels more like a generic shonen (with great art and choreographed fights tho). However, even as a simple shonen, Murata could have profited of the better pacing, suspense and building of One's webcomic.
