Depends if you want/need more braking force. I run 203/180 all year round.
Downside (and it can be quite substantial) is weight, it goes up with almost the cube of diameter but don’t be tempted to swap to lightweight rotors with large cutouts, IME they offer less power than just going smaller so not worthwhile unless you already are on 160/140. Lever feel is more on/off. And pad life*.
Upsides are lots more power**.
*small rotors run much hotter, I used to run 160/140 and they would fade even at a trail center. But pads would last a full winter as the surface hardenes once heated (aka bedding in). Barely worth bothering with now, just run cheap sintered pads.
**More of a problem on 29ers and fat bikes as the brake size in effect has to be scaled with the tyre diameter to get the same power at a given speed (power =frictional force x disk velocity, 29ers rotate about 10% slower so 10% more disk offsets that). So 203/180 on a 29er doesn’t feel that much different to how 180/160 did on a 26er.