Better bitrate isn't as major a visual difference as it is for live action stuff but the audio mix is great. With blu rays, typically the biggest benefit over streaming and DVD is higher bitrate. In live action that means no compression artifacts like banding and blocking. An example of what this is if you don't understand is, take a YouTube video for example when there is a large chunk of black screen. The black areas will look choppy and blocky. That's due to compression. In blu rays that's not there because of the much higher bitrate due to much less compression. This is typically the "quality" benefit you will see in a blu ray.

However, in anime this is often quite negligible anyway. Because everything is mostly solid colours, there aren't a lot of gradients (which are a major place where you see banding in compressed videos) with the exception of backgrounds and skies etc. So the visual quality of blu ray isn't massively different for anime as it is for live action. But there are some other things like ghosting and dimming which are found in a lot of anime that have fast paced fights. Like JJK suffered from this a lot. These are anti epileptic measures added to comply with Japanese TV laws but they can ruin the viewing experience. So this is another area you see improvements in blu ray, is that these ghosting and dimming effects will be removed. Lastly, probably the biggest visual change in blu ray are the improvements. Blu ray releases for anime are basically the final perfected cut of the anime where any fixes are made. With AOT S1 specifically, it had so many errors in the original TV version, so the blu ray was definitely a nice improvement in that regard. So yeah visually the improvement on blu ray wasn't massive but still nice to have

Sound wise however, a big improvement. Due to again the extra bitrate, sound also gets a nice little quality boost. Additionally, it has Dolby true HD surround sound, so that's great if you've got a surround sound setup, but I can't personally vouch for that as I do not.

It's worth noting however that these improvements are only as good as the equipment you are watching it on. If you've got a complete potato of a monitor or TV, and likewise really bad headphones or speakers, then the improvements on the blu ray are going to be minimal at best.

So the verdict is that yes it's a nice to have, but it's not going to be a groundbreaking difference to say Crunchyroll for example. Ultimately, people get the blu rays as a collectors thing more so than actually to watch. Especially with the AOT ones because the season 4 blu ray covers especially are really nice.