Depends upon personal choice. Food wise too, it all depends. My personal experience says KSK food is a big turn-off, but again it depends. And if u dont like food, the options are limited, as this train has limited stops, which is not the case with GT. Secondly, GT terminates at NDLS, which is a big positive, in that u can avoid d-boarding at Nizamudin, in case u choose to travel by KSK. Rest u can decide.
About GT food, I have no comments to offer, as i have no such experience in recent past.