Which one is better and why Lenovo or Samsung?

I would go with Lenovo, they are very good for people who use their PCs for work. If however, you're planning on just watching videos on Youtube or loging in to Facebook it doesn't really matter that much.
You have to be more specific. What do you need this information for? Are you planning on buying a specific product? If so, what would you like to do with it?
Your question is so broadly asked that you could aswell ask: what is better: an apple or a pear?

According to me both are equal. Samsung is more popular in phones and lenovo in Computers and laptops