"Nice" is a (rather overused) word to indicate something is merely pleasant or agreeable. "Beauty" has a stronger meaning, usually for the appearance of something or someone, but often you'll hear "beautiful person" used to describe a person's personality.

The adjective 'nice' can be used to describe things and people. - a nice day (weather): lovely, fine, warm, sunny - some form of entertainment (a nice trip): enjoyable, pleasant, amusing, delightful, fun - accommodation (a nice hotel): comfortable, pleasant - clothes: smart, good, stylish - food: appetising, delicious, tasty - a nice job: efficient, competent, fine, good, excellent... - a nice person: kind, helpful, generous (or friendly, pleasant, charming...) However, 'nice' can also be used to mean 'beautiful' when describing nature (scenery, views, etc): a nice scenery: beautiful, picturesque, lovely, attractive

When 'beautiful' is used to describe looks and appearance of people it means being aesthetically pleasing to the eye. The meaning here can't be compared to the meaning of the word 'nice', which refers to pleasant traits of one's character like being friendly, delicate or respectful ( the exact connotation depends on the context). When you are talking about a person, saying he/she is a 'beautiful person' you are talking as well about the personality as in 'nice person'. It doesn't refer to the beauty of the looks and appearance. The main difference here between 'nice' and 'beautiful' is that the beauty of a character is extended to many traits of the personality all together resulting in describing the person as 'beautiful'. It is deeper in meaning and more general than calling someone 'nice' ,that could relate to a certain behavior or conduct. You could call someone 'nice' when he/she does you a favor or smiles at you , but to call someone 'beautiful' you are referring to the whole character and you have probably experienced a lot with that person to describe him/her as such. When the talk is about 'beautiful people' in general , it refers as an expression to rich, fashionable people in high society; it is a peculiar meaning here, which differs totally from describing people as being 'nice' ,which means they are pleasant, kind or friendly. When describing a thing saying it is 'beautiful' it is always a degree higher than using the word 'nice'. 'A beautiful day' is very pleasant and highly enjoyable, while 'a nice day' is just a pleasant day. Those were just some of the main differences in the usage of both words as adjectives describing people and things.

Beautiful is when someone or something is very pretty in appearance. Nice usually refers to someone's personality (and it can refer to a thing, too), but does not only focus on appearance. A nice person is someone who is very kind to others and makes a lot of friends, whereas a beautiful person might not be kind or make a lot of friends. So beautiful typically refers to the surface appearance of something, whereas nice refers to someone's personality beneath the surface. When you talk about objects as being beautiful or nice, though, they usually mean about the same thing.