For starters, the Bedrock codebase is written in C++ as opposed to Java. This is a very important detail - as Bedrock is not held back by the Java Virtual Machine's piss-poor performance and CPU resource consumption. This lack of need for allocation allows the game to be able to run instructions at a much faster pace, being able to read and parse chunk data almost instantly on most devices.

The Bedrock codebase also refactors how chunk loading worked compared to Java edition. In Java, chunks are small 16x16 (X, Z) areas of terrain - notice the absence of a Y coordinate. Due to the lack of Y calculation, Java edition is loading 16x256x16 chunks, which can be a major memory hog. In Bedrock, chunks are calculated in all 3-dimensions, 16x16x16. This means less memory needs to be reserved on a per-chunk basis. On the subject of the 2D vs 3D chunk management, Java edition is frequently exploited due to it's large chunk sizes. If a chunk exceeds 1MB, you can execute duplication glitches. Every other week or so a new method to hit this 1MB limit is revealed and is used to troll server members. If Java both fixed their renderer and switched to 3D chunk management, this would not be a problem at all.

Now, the Renderer - Java's edition renderer is HORRIBLE. It has been the same since early alpha. It is sluggish, sometimes unresponsive, and untrustworthy. Flying to the sky in Java, you can clearly see how long it takes for the Renderer to manage chunk rendering, it can take ages and the lack of fog (a Bedrock codebase feature) makes this abundantly easy to spot. Java has been in need of a Renderer rewrite for years now, performance slowly worsens with every update and the Renderer takes longer and longer to keep up to the player at large distances. It's ridiculous. The Bedrock team is not afraid to rewrite large bits of their game - they actually made a new Renderer a few months ago (RenderDragon) and are in the process of rolling it out, making the game even FASTER.

Java edition's team is also quite incompetent, I respect the work they have done but it really shows that they care more about squeezing as much content as they can in the game no matter how well it works. Java 1.15 promised improved performance - but all around the game consumes 300 additional MB of RAM, which is absolutely ridiculous.

Finally, I want to address Bedrock's in game store. This is what steers a lot of Java edition plays away, but it isn't bad at all. It is a great way to support creators (only ~10% of what you pay goes to MS, and it's just to keep the server running) and for console players to get an endless stream of custom content so they don't feel out of place in multiplayer servers for their skins. I was actually really close with someone who relied solely on the Mincraft Store financially, he was an amazing guy. Minecoins are sorta dumb but it's a way to universally hold currency so you can sync purchases and money throughout all of your devices.
I understand Bedrock lacks some Java features and Redstone is a bit shakey - but to be honest, I don't think the Bedrock team is 100% to blame for these lack of features. Most people who complain do it through Reddit and not the official MC feedback page, which is where the Microsoft branch of Mojang stated suggestions are considered the most.
tl;dr - bedrock is much faster, team is more competent, ability to support creators is cool