It is good, you have not joined the new company. So, you can write back to them saying that either due to personal reasons or better prospects, you are not able to join them.
It is courtesy from side to inform the 1st company, so they can roll the offer to next candidate in line, rather than keeping them in dark.
How will the other company know, where you are joining and how they give you any trouble is not understood though.
But remember one thing, don't keep salary alone as a criteria to join a company. Every company has its share of politics and problems.
If your Habitual job hopper, just by seeing one's resume it will be known. This also can form a basis to reject in a new company, even if you have done well.
And In fact i am not focussed on salary sir. Two companies are paying same salary only.
But I Like to join yyy.
Peace of mind will be better than xxx company than pressure of mind for same salary.
thank you for everyone who gave hands when i was in question.
This will save you a lot of unnecessary headaches later on, and you will reflect that you possess and integrity and honesty, among other things, as positive traits.
For some young and curious minds taking on to jobs for the first time, or for switching jobs later on, remember to see does your passion equate with the skill you need to carry on your job, the growth potential in the long term, and that you are at home with the work environment and culture.
Honesty does not and cannot entail problems. You will, in fact be appreciated for being fair and just. If you come up with a false reason, that guilt complex will haunt you endlessly.
Be honest in all things at all times - be they professional, social, familial.
Hope these lines help