It would depend on the size of the paycut (A large percentage?), and the advancement potential in the position. Why start a new job at the top of the pay scale, and at the top of the ladder?

You may be happier at the new position, and gain valuable experience to further your carrer. But it would not be optimal to start a new position where it takes two years to get back to your current wage if your not learning valuable skills to help your earning potential.