Yes, it's always better to have more than 1 kettlebell and it's also great to have 2 kettlebells of the same size/weight. With double kettlebell work, you are loading up more weight, hence, making it more difficult and increasing the strength and growth results. Using 2 kettlebells to perform an exercise can add more weight overall, but 1 heavier kettlebell weight can give you more bang for your buck. For example, pressing 2 x 16kg or 1 x 32kg. When pressing two 16s you are overall pressing the same weight as you would with one 32, but with one 32 you are adding double the load to one arm.