有 is kind of informal verb, we always say the word in our daily life , like 我只有一只笔，但是我不能借给你，因为我也需要（i only have one pencil but i cannot lend it to you ,cuz i also need to use it to maybe write a paper or something else ） but 拥有 is more like formal verb , we often use the word when we write something , obviously ,we seldom use it in our daily life , and the word are supposed to be attached with assets（ like 房子，飞机，公司) also you should know that when you are allowed to use the 拥有， then 有 can be used as well which means the word 有 do have a broader range of usage ,compared with 拥有

有 has a lot of meanings.it can be a verb,a adj,a adv.拥有 is a verb. and when they mean possess or have or own , most the time you can switch each other. Actually, u can use 有 instead of 拥有 most the time, but not the other way around.

有= have. 拥有=own I have you which means you stay with me. I own you which means you are belong to me.

有：have 拥有：possess