Are the BEST 2 songs actually any different from the original?

[Melrose]

Are the BEST 2 songs actually any different from the original? I know that in the commercials, etc. they said that the songs were remixed, but comparing it to the originals they sound, well, 100% the same. IS there a difference? Maybe just with certain songs? A BEST was resung on the old songs, but since that wasn't done with A BEST 2 I thought the instrumentals had gotten some kind of remix. I just don't notice it. Has anyone else noticed a difference between the A BEST 2 and originals?