Two great yet different sounding preamps, the CT 5 offers more detail the SLP 05 is a bit more liquid so it depends on what you are trying to bring out of your system.
The other things to consider is that the CT 5 uses only two tubes so is going to be quieter and very easy to maintain.
Also CT 5 offers totally modern feature set, remote imput switching, theater bypass while the Cary only offers remote volume.