This has been discussed many times before but let me recap.
1. The number of pits that make a bit/byte is much more in a DVD as compared to a CD. Consequently, a DVD read/write head has to move in smaller steps to read the larger number of data pits. How does this matter? By the simple fact that a read head is a electromechanical device and is always prone to making errors. While reading from a CD, it could skip a few pits giving you erroneous data.
2. The amount of electronics in a CD player is much less, again leading to lesser interference.
3. A DVD player does not have a very good DAC, as it is expected that the decoding and DAC conversion will be done externally. A CD player, on the other hand, has a very good DAC as it mostly sends analogue data.
4. Given the price and the amount of material inside, a CD player is usually made of better parts. Some of the companies such as Cyrus make their own drives. A DVD player is a mass market item, and in general is just assembled from outsourced items. Though Pioneer is an excellent DVD player, if you open it, you will find more third party labels than Pioneer inside.
5. A DVD player has a short life cycle in terms of design and technology. A CD player, on the other hand is usually designed to last for 5 years or more.
Enough? Of course, whatever I am saying makes sense if you are serious about music. As Spiro and other have said, companies such as CA, Oppo and others have made DVD player that double up as excellent CD players also. I use my Oppo 983 only for playing music.
If I remember right, someone is selling a Oppo 981H for 8K. That is an excellent purchase.
Cheers