There is a significant difference in picture quality between a 4K BluRay player and a standard BluRay player when used with an Ultra HD TV. A 4K BluRay player is capable of playing 4K Ultra HD discs, which have a resolution of 3840 x 2160 pixels, four times the resolution of a standard BluRay player. Additionally, 4K BluRay players often have features such as high dynamic range (HDR) optimization and support for advanced audio formats, which can further enhance the viewing experience. On the other hand, standard BluRay players can only play standard BluRay discs, which have a resolution of 1920 x 1080 pixels, and may not support advanced audio formats. Therefore, if you want to get the most out of your Ultra HD TV, a 4K BluRay player is the better choice.