I DARE you, change my mind.

Pretty sure they were both rated 13+ tho.

no, undertale is rated 10+, deltarune is rated 13+

Ok, well here's how they are separated officially. One game puts the focus on all the choices you can make and gives you a bunch of different endings because of them. The second allows you some mockery of a choice, but no matter what you can't change your ending.

How is undertale not 13+? I don't think a 10 year old should see photoshop flowey

that's not really innapropriate or anything though

But it is something the esrb puts it with age ratings.

true, but there's not that much scary stuff.

Good point. But the esrb gave gta san andreas an adult rating bc there was some nude textures that can only be accessed with hacks.
In other words, even just a single section changes the whole rating

some frightening scenes is a lot different than nudity.

Imma restate my last sentence
Even just a single section changes the whole rating

I think it has slightly more "curse words(?)"
I guess, like damn and hell