which is better maths or chess ? and why its better

Chess as an activity is a fusion of game theory (a branch of mathematics) and sociology (descended from psychology -> biology -> chemistry -> physics -> mathematics), so it's like asking whether a sandwich or a peanut butter and pickle sandwich is better.

I witnessed a horse giving birth once and I've never felt more alive.

If you had to choose one, math is surely the way to go. I would also choose math and life rather than spending 4-6 hours/day on chess to become a master.
Becoming very strong at math opens up good-paying careers and allows you to understand financial situations so that you can get more for your money, etc. Becoming a master at chess does NOT usually provide a good living.
On the other hand, doing what makes you happy is important if it doesn't reduce your future happiness and standard of living. So chess plays an important part in many of our lives.

As a hobby, math is slightly better only because you can play by yourself and have a lot of fun. (For chess, you need a partner, be it human or machine.)

From a career perspective that's weighted towards financial earning power, it's abundantly clear that being proficient in mathematical problem solving is a far better choice than to be proficient in chess.
The career financial gains from being analytical in a STEM profession has a far greater ROI than all the time and money spent on achieving chess mastery.
And I say this as someone who really loves chess. However, there are some special people who have achieved success in both chess and in fields outside of chess. But that's really rare.