Your competitor is paying his employees more than what you earn for the same tasks :1/ you quit ? 2/ you ask for raise ? 3/ you continue and you don't care?

i dont care at all. at the onset this is what i got what we have agreed during my interview and i accept it. 

It is not going to be  black or white; look at the full picture and compare the full package, job security and future advancement. Give points to each of the3 factors depending on its weight  and then join /stay in the  company which gives you higher points. Negotiation on packages with your current employer rarely works.

Raise a question if everything is same.

If I am sure I am worth more than being paid will try my best through my work to impress my current company to take notice and lay me in line with market. If the company is understanding they will correct however if the attitude is indifferent then I will find my way to a place who recognize my worth. 

First thing to do is ask for a raise, you should always be very clear in your requirements and make sure that your employer (or manager) is fully aware that you are not satisfied with your current status, if you are faced with a negative feedback, then you should consider quiting and search for other alternatives. 

i don't care

Keep ongoing in the good work and don't wait reply from the employer in order not to shock the fact that the employer does not care about you to stay or go, think well before you decide to leave and think in the employees who get lower salary from you , continue the do the good work and you'll see the difference in the future and you will see that your way of thinking is different from others and this make you better from others, don't watch what on the hands of the others.

avoid to destroy your self 

I will review the whole situation and decide accordingly. It is not only the salary, but many other things like work safety and benefits.