In my experience bitcoin cash is a fork of bitcoin even BCH is faster and cheaper to use due to larger blocks but still it'a seen that most of the people are using BTC than BCH so why is bitcoin doing better than bitcoin cash?
There are multiple forks of Bitcoin which create altcoins, but there is only one Bitcoin. The question of whether larger blocks are better than smaller blocks seems to have been settled for now - Bitcoin Cash only has a fraction of the market capitalization of Bitcoin. Until scalability becomes an issue again, do not expect Bitcoin Cash to increase in value.