What is more important for both India and Pakistan, the World Cup or the Asia Cup?

 It is definitely the World Cup.

Asia Cup has only 3 major teams who have won till date that are India, Pakistan and Sri Lanka. There is not much competition.

Whereas in the World Cup there are many teams and every team has fantastic players. Many countries have won the world cup and Pakistan and India have won 1 and 2 times respectively.

In short winning the World Cup is much much more valuable then winning a Asia Cup.