A lot of people like to say that Ron's second house is either Hufflepuff because of the movies or Slytherin simply because of the scene with the Mirror of Erised in the Philosopher's Stone, but in my opinion that's not it. Movie Ron is not Book Ron, and Ron does not aim to be those things that are shown in the Mirror of Erised, he simply desires them. His aim is towards helping his friends, and having fun playing chess or Quidditch. He is more quick-witted that people give him credit for, and more knowledgeable as well. He also had a certain wisdom to him, knowing things or perceiving them in such a way that he sometimes predicts things that will happen. Like predicting that Lockhart was a fraud. He even told Hermione that someone as powerful like Dumbledore could be tricked by a really clever Dark wizard (Grinderwald).
And Hermione would definitely be a Slytherin. Outside of the fact that she literally created two organizations with the aim to defy an authority (S.P.E.W and the D.A.). She was determined, resourceful and clever, which are all Slytherin traits. She was also more vicious in certain aspects that people sometimes ignore. Marietta Edgecombe comes to mind, as well as Rita Skeeter, or sending Ron those birds.
If they weren’t in gryffindor, Ron would be a ravenclaw and Hermione would be a slytherin.
ron is logical and strategic, often has great and practical ideas. hermione is ambitious, resourceful and determined. it makes sense to me.