Should You Read the Manga or Watch the Anime?
First of all, I just want to point out that manga is black and white - there's no colour, well… except sometimes you get it from the cover art and special spreads if you're lucky. Some think this is bad, but personally I don't mind because it allows the reader to interpret and superimpose what they think the colours are. For example, we can reference JoJo's Bizarre Adventure, where both the manga and the anime constantly and radically change their colour schemes. At least looking at the JJK manga vs its anime adaptation, you can see that our main protagonist's hair colour is different because it's red in the anime whereas manga readers would have interpreted it as blond since that's how it was shown in a few colour spreads.
Sometimes, we can get pretty unfortunate results from anime adaptations of even our favourite shows. Just take a look at the long-awaited One Punch season 2 by J.C. Staff… how I wish Madhouse animated the second season as well as the first. Fortunately, we were blessed with MAPPA and they absolutely killed it with the anime adaptation, so there's nothing to worry about here. Not only is the animation amazing, the art is also stunning - it's clear that they were dedicated to their work and had great direction.
Even though it stays true to its source, the art style does differ slightly from the manga because it needs to be adapted for TV. Other than that, you should know that the artist's style itself can change and improve throughout the series as well. Even more than this, you should know that an adaptation will never be 1:1 - it's simply impossible to achieve between different mediums because there's always going to be changes in order and pacing to flesh out the missing details. However, with adaptations like this we can get the benefit of things like anime-only, exclusive scenes. Overall, we need to remember that the animation and still manga panels leaves room for interpretation and flair about the motion and movement going on in the scene. I think MAPPA did a great job and showed great awareness and emotional depth regarding the source material as evident by their adaptation. For example, in the anime they spent more time on the backstory of the grandpa and the connection to the protagonist, instilling more emotional depth and meaning into their relationship and the sequence of events that happen after this scene. Overall, the anime does tend to lack a bit on the supporting character's personal stories since there's only so much screen time available and this was a relatively short anime adaptation. Don't get me wrong, I actually like that aspect because they kept the pacing very fresh and things never really felt like they were moving too slowly.
Whether you read or watch JJK, you can quickly binge everything so far and catch up. Once you're up to date, you can eagerly await the next chapter, volume, episode, or season to be released. Obviously, anime seasons are usually spaced 1-2 years apart and release an episode each week for 3-4 months. Meanwhile, a new manga chapter is released weekly in Shonen Jump magazine, but the downside is you'll always be stuck on the worst cliffhangers after a relatively short chapter and be left thirsting for more. As you can see, there's pros and cons associated with waiting for either the manga or anime. However, I will point out that it's usually a lot faster to read the manga compared to watching the anime. To help you get an idea about the correlation to the two, you can typically expect a standard 20-30min episode (with an opening theme and end credits) to adapt about 2-4 chapters. This varies based on the content of the chapters because dialogue scenes will take up a lot of panels in the manga but happen relatively quickly in the anime, while fight scenes in the manga can be short or long but always take a considerable amount of time in the anime. This is especially true for JJK and the gorgeous fight scenes MAPPA animated for this battle shonen.
Conclusion
To summarize, both reading the manga and watching the anime have their respective pros and cons, but it's ultimately up to you to decide - I was just trying to help give some valuable knowledge and information. If you really want my final opinion, I'd say do both! That way you get the best of both worlds. In all seriousness though, I do recommend both reading the manga and watching the anime; however, if you only have time for one, then I'd recommend the anime. The MAPPA studio just did such an amazing job with the adaptation that all three of its seasons so far are of superb quality, I can't not recommend it. The anime looks more modern and cleaner, so most people would say it looks better especially when compared to the original black and white manga drawings. This being said, the manga is nothing to scoff at - by reading it you get the original and pure content, both story and art. Although it's not the same as the anime, the art is stunning in its own way. Hopefully, you end like me and read the manga after watching the anime and then stay up to date on both. Its popularity is sky high and there's no indication of anything dying - heck, they even released a movie based on the series' pilot Jujutsu Kaisen 0. By the way, I totally recommend watching and reading this too (and it's a prequel movie). In case you didn't know, Jujutsu Kaisen is both authored and illustrated by Gege Akutami. They are an exceptional artist that effectively utilizes dynamic shot composition, expressive characterization, and imaginative depictions of sorcery and combat to bring texture and electricity to their panels. You're missing out if you don't see where this series started.
If you're interested in knowing more about the world of Jujutsu Kaisen, check out my other pages that detail more about cursed energy, curses, and special techniques like Black Flash! There's also a Jujutsu Kaisen Fandom wiki for the series that has literally everything documented, so if you ever have a question and can't get in touch, here's your best bet.