The discs of the 80's were generally the worst (with some exceptions). Current discs in many cases are just as bad and so much of the engineering work down now days on popular music is mixed as much for MP3 performance as it is for full resolution and full frequency. This obviously is not good.
Additionally, most of todays mixes are much louder than older discs as this has too become part of the modern mixing schemes.
Jaybo is 100% correct in that it really needs to be considered on a title by title basis. Dark Side of the Moon for example has something like 8 different versions out (including SACD/DVD-A/HDCD/Redbook). I would only consider adding or replacing based on careful reviews and generally only for the music you enjoy the most. Personally, if I am too replace a Redbook with a Redbook, I want to see that it has been re-mastered versus just a new release of the same mix.
Additionally, most of todays mixes are much louder than older discs as this has too become part of the modern mixing schemes.
Jaybo is 100% correct in that it really needs to be considered on a title by title basis. Dark Side of the Moon for example has something like 8 different versions out (including SACD/DVD-A/HDCD/Redbook). I would only consider adding or replacing based on careful reviews and generally only for the music you enjoy the most. Personally, if I am too replace a Redbook with a Redbook, I want to see that it has been re-mastered versus just a new release of the same mix.