Bluetooth, just like any other technology, evolves, and newer versions are usually better. The only downside is that you can't upgrade it in a cell phone or any other standalone device, but you can do this on a PC.
That's one point, though PC is getting too old for our needs these days (except for those who play lots of games at home, I guess). The issue is the audio files aren't exactly coded to be optimized according to the Bluetooth generation. If the data transfer is no different, then the sound quality we perceive also stays the same.