If you have a decent home theater setup it makes a very noticeable difference in both picture and sound. Good bluray and 4k bluray releases often have lossless audio codecs, and currently no streaming service has this. Although, sound differences might be more due to mixing differences. Streams tend to mix in a way that prioritizes the 5.1 sound still sounding good to people using the lowest common denominator setup.

But also the bitrate alone should tell you something. You will typically get around 15-20 Mbps for 4k streaming, and often lower, though Apple's service apparently will occasionally hit up to 40 Mbps. 4k discs have a bitrate of around 128 Mbps.