English willow is the best wood for durability and quality - it does cost more however than Kashmir and English nutured willow.
Some people prefer heavy bats, others prefer light. It depends on your batting style. Lighter bats are generally preferred for openers, quick pitches, players that are good pullers, hookers and cutters, whilst heavier bats are generally preferred for middle order batsman, slow pitches, players that are good drivers.
Best advice I can give is try lots of different bats out at the store and see what feels best for you.