Ordinarily I'd have chosen the clay 'clumping' type of litter, but my cat was a rescue and I was advised to use the same litter as he'd been used to at the shelter.
Having now tried the woodchip litter, I wouldn't go back to the clay variety. Woodchip litter has a pleasant fresh smell, it's easy to use, economical and eco-friendly:
The pellets disintegrate in contact with moisture, so the 'used' part collects at the bottom of the tray as sawdust. This gets scooped out to go on the compost heap, and any poos just get flushed down the loo. You couldn't do this with the clay type, and it beats filling up the dustbin with bags of used cat litter. It doesn't track on the cat's paws either - another plus.
Just bear in mind that a 30-litre bag is HEAVY. I felt sorry for the postman staggering up the drive with it, however he shouldn't have to make the trip too often as the bag looks as though it will last for a while.