be important to sb.:……对sb.而言是很重要的,强调对某人很重要的东西.
eg.
What is important to you is also important to me.
对你重要的事对我也重要.
Money is important to me.
be important for sb.（to do sth.）：某人……是很重要的,强调做某事对某人的重要性.
eg.
It is important for you to get there early.