What is the difference ladies in with these two bottles?

Cindy💙💙

So I've been getting ready for our babyboy 💙💙10/25 and I recently bought the starter kit of avent blue classic bottles, now I see a lot of avent natural bottles this is my first time using these bottles. Ladies what is the difference because I really don't see much other then shape of the bottle?🤔🤔🤔🤔🤔🤔