I started comparing the mixes of some of the titles that appear on both of these releases as suggested by someone here and found the following. The first one I did was "Happy Christmas (War is Over)". There are subtle but interesting differences.
The 2003 mix has John in the fronts but not the center. The center is strum guitar and a very clear bell and drum kit. There are also echo voices in there for the chorus, but if you want to hear the glock (or whatever they were using for a bell, this is the channel you want!)
The 2018 mix has John in all 3 front speakers, and the bell is moved to the rears. The overall presentation is about the same on both versions with these exceptions.
At the beginning, when John and Yoko wish their kids "Happy Christmas", the call outs are in the rears on the 2003 mix, and in the fronts on the 2018 mix.
Here are the wav shots, they don't look that different, but you can see there is no lead vocal in the center of the Legend mix (Lower WAV file below).
The 2003 mix has John in the fronts but not the center. The center is strum guitar and a very clear bell and drum kit. There are also echo voices in there for the chorus, but if you want to hear the glock (or whatever they were using for a bell, this is the channel you want!)
The 2018 mix has John in all 3 front speakers, and the bell is moved to the rears. The overall presentation is about the same on both versions with these exceptions.
At the beginning, when John and Yoko wish their kids "Happy Christmas", the call outs are in the rears on the 2003 mix, and in the fronts on the 2018 mix.
Here are the wav shots, they don't look that different, but you can see there is no lead vocal in the center of the Legend mix (Lower WAV file below).