Differences between the two phrases?

Both the sentences are correct.

Possessive pronouns are, in short, exactly that: they are the pronouns that help us show possession in the English language. Usually to show possession, we have two options that are grammatically correct. First, we can use an apostrophe and an s: 

 In singular possessive terms, place the apostrophe before the "s." This will indicate ownership by one person or thing. For example: I would you rephrase your sentence as "Sara's portrait".

Experts  tell us to avoid prepositions by using possessives instead.

The success of the student was largely attributable to their hard work and dedication.

The students' success was largely attributable to their hard work and dedication.

I have been taught by Mr. Jeff, an expert of grammarly,  to use  possessives in this way.