I work in Company A and I'm kind of the star there (I feel that mainly due to political reasons). Recently I received offer from Company B and I decided to accept it. HR department in my current company push me to review my decision and propose them conditions under which I would like to stay at company.

I feel that offer from Company B is much better for my career (project is more interesting, company is also a better suit for me), but I don't want to burn bridges. How can I respond?