The 12x binocular has a higher magnification than the 10x. This means that you will be able to see further with the 12x binocular. However, the 10x binocular has a wider field of view, meaning that you have a wider vision in the shorter distance that the 10x binocular can see. Assuming both binoculars have the same objective lens diameter, the 10x will do better in low-light areas.