The best train between KHI and Lahore is:
1) Greenline
2) Karakoram
3) Business Express
all above have Business class and less run time.
Night coach express is good too but they have AC Lower, not business class.
Tezgam has AC Sleeper also but its running time is more.
Edit: Oopps... just saw u wanted to travel in economy.. then only choose Karakoram or Night coach express.