Larger rotors provide more power at a heavier weight. Some frames and forks have a maximum or minimum rotor size they can accept. Changing the size of your rotor will require a suitable brake mount. Learn how to choose the right brake mount for a new rotor.
1.8-1.9mm thick rotors will fit any brake caliper. Rotors thicker than 2mm are only compatible with specific brake models. If in doubt, check your old rotors to see if they list a size over 2mm - if not, choose 1.8-1.9mm.