They mean the same and you can use any one of them to express ownership. What is the difference? The difference lies in theit position as part of speech. لي consists of ل which is حرف جر and ي which is the pronoun of the speaker. While عندي and لدي are adverbs which are used to express possession. عند اسم او ظرف لمكان وزمان الحظور. لدى ظرف مكان جامد بمعنى عند. And ي belong to the speaker or the doer of the action. I hope that helps.

This is the explanation of Madinah book 1 lesson 10. عند is for separable things (book money pen) and لي is for relations and body parts(inseparable things).

there isnt different between both but عندي used more

أهلا آبي عندي ولي بنفس المعنى )أما الفرق في اللغة فبين (عندي) و (لدي لدي : معناه ان الشئ حاضر بحوزتك It means you have the thing right now within the place that you are in أما عندي فتستخدم لما في حوزتك حاضرا أو غائبا This means that i have it but either with me right now or it is in a safe place elsewhere

Hi Abbey ! there's no difference not even a small one they both mean ownership as you mentioned but maybe the one ( عند) is more used in most Arabic countries than the other one I think (li ) is more used in Egypt . In Syria we say عندي