I have always avoided this place due to it having been owned by the people behind the Prime Table (formally of Rolling Meadows) which I always thought was garbage. In the same area as Chicago Prime is Mortons, and not too far away is Fleming's (Lincolnshire) which I thought was pretty comparable to a downtown steak house.
If you are going to take out clients though, I would recommend taking then to Nine (Chicago). While it may not be the best steak house, it is the glitziest. People usually come away pretty impressed by the meal and more so the scene.
Nine
440 W Randolph St, Chicago, 60606 - (312) 575-9900
Flemings
960 Milwaukee Ave., Lincolnshire, (847) 793-0333
Mortons
1470 Mcconnor Pkwy, Schaumburg, IL 60173, (847) 413-8771