So I don't think I can spell out exactly why this episode is so special to me, but it is. I think part of it is that we are literally watching someone who has spent the better part of this series trying to murder two characters, now going on a rollercoaster with them. But, that's not all.
I think a large part of why it's special to me is the tablet. The extent to which Peridot appreciates the tablet Steven gives to her is just beautiful to watch. You can tell it means a lot to her, and I think it would mean a lot to me if I were in her position. Not even a technoalien stranded on another planet, but just someone that's lost and doesn't haven anything. It's as though, when Steven gives her the tablet Peridot is becoming herself again, she is reconstructing her identity, and it is so wholesome to watch this happen at a theme park, and so sad to watch amethyst trying to take it away from here.
This is just my best guess though, I think that the true answer is hard to put into words, but there is definitely something special about this episode - to me at least.