Small city with a nice vibrant old town, many small streets and alleyways. Also more history here than in Samarkand. Feels like the Uzbekistan version of Istanbul.
Bukhara is a great place to be. Feels more local and authentic than Samarkand, also more history than Samarkand. The main open spaces are packed tighter together and feel much less commercial than in Samarkand. Everything is closer together and much more walkable, you won’t even need a Yandex. So definitely, Bukhara will feel more fun. And also, it’s cheaper here.
2-3 days is a good amount to enjoy.