Is the Xbox Series X worth it?

Would change from the One x

Not for me yet. I also bought the One X and therefore haven't bought a Series X yet

For me already by the loading time and quick resume

As you can see, there's no universal answer to this.

For me in any case and I also owned the One X before.

Not only that, the games, depending on either running with more frames or higher resolution, optimized games look a whole lot better.

Then there are the extremely fast loading times and quick resume.

You have to decide for yourself whether this is worth 500 euro to you at the moment.