Somewhat. You sort of need both in a modern first world society.
Neither, or both are better. It depends upon the society you live in and are used to. Unfortunately the people under each system seldom really understand the other system and either see only faults with the other, or only see the good side of the other.
I would say that, since the 1930's, there has been no fully capitalist system.
For example: America is commonly thought of as a capitalist society - but has plenty of socialist programs such as Welfare, Social Security, Food Stamps, Farm Subsidies, etc, etc.
On the other hand, it's easier to have a fully socialist society - because the government just forbids private industry. Usually, that is found under a dictatorship or communist government.
An example of a socialist economy changing to a mixed economy, is China.
That is very hard to say. Each one has it's advantage and disadvantage.
It was Margaret Thatcher who said "the problem with socialism is that sooner or later you run out of other people's money"!