More money can buy you more security (unexpected medical bills...), free time (why not take 6 months off to travel?), and opportunity (I'm gona fund my own startup!) that OP might not be considering at the moment. With the future being uncertain, and all other things being equal between the jobs, it would be silly not to take the money.
Worst case, you shove it in a savings account/index fund and never think about it again.
The implication of my post was that if there was something about his current job that made him really, really happy, he didn't necessarily have to even look at the other job.
Getting a modest raise frequently happens, but doubling your salary in one career jump is pretty rare. Doubling a salary is too big of an increase to ignore for most people.
Why is that? Is life always better with more money?
If the OP is happy with the amount of money he is already making, why should he look for ever-higher salaries?