If you compare Joan to Jane and Joe to John, Joan and Joe are usually stronger because they end more pleasantly.
Some other elements of sound you can consider: Characters immerse your readers in your world.
The Manhattan Mangler is probably a loose cannon with tattoos, long hair, leather jackets, etc.
As a rule of thumb, once you have used a given letter to start a character’s name, you can’t use it again.
If your work is long enough that you name 15 characters, then you can start sharing the letters of minor characters who appear in completely different parts of the book.
Character names serve several important roles, like differentiating characters and evoking an emotional response from readers.
Readers use names to tell characters apart, obviously.