The support materials (instructions) these sets come with are identical, the biggest difference is the storage container. The wooden rolling bin is the only option for 1000 pieces and the 800 piece set has 3 options: canvas bags, plastic tubs, or smaller drawstring bags. The number of KEVA Balls that come with a set is directly related to the number of planks in the set (more planks --> more balls).

The short answer is, the more the better. People usually wish they had more. People build until they run out of KEVA planks so if several people are building at one time, they'll run out of planks sooner.