Just began Katawa Shoujo so I can't accurately compare the two just yet, but I feel like there are some similarities in the ideas behind those two games. Can't say much more without spoilers, but To the Moon is cheap, and you can play the first hour for free, so you should try it.
It has little interactivity, just like a visual novel. It's just centered on exploring the levels rather than exploring branching paths. I really liked the game, there are genuinely touching moments in the story, with simple but engaging visuals and a great OST.
It's great to see games trying things on the emotional side. I was a bit skeptical about KS at start, I'm not really into visual novels (still I did like things like Phoenix Wright and the text sections in Nier and Lost Odyssey a lot), and when I saw the team was from 4chan, I... uh... well... was puzzled. But the game speak for itself so far, it's well written and all the girls are interesting. I seem to be on the beginning of Emi's path and I really want to see what's next. Without this thread I probably wouldn't have played it so thanks guys !