Best of the range
Having tried the Classic 3 in 1 and Diamond Care varieties, as well as a few other brands, I am sticking with the Micro. It has the best clumping power (as long as you pile it at least a couple of inches deep in the litter box), very little tracking, a reasonably-low amount of dust, and it does last a very, very long time. The Diamond Care range seems a tad better in terms of odour control, but this has never been an issue for me. I have just one cat, and clean the box 3+ times a day.