In all fairness to both sides. Good food isn't a product of the tools necessarily. My opinion is, whichever accomplishes your desires in the least expensive way, go that way. My husband purposefully purchased a cheap off-set firebox w/smoker, because it is more about the food you have available and the technique in which you prepare it. I believe the cavemen had some really good roasts!
I say buy the grille w/cheap accessory.
Regarding company, I feel the same way..."how to accomodate that many people w/one small grille?" It's okay to go two rounds. If you are planning a dinner party, then really plan. Plan to do all pre-preparations the day b4 (chopping, measuring, lay out your flowpath...etc.) Start your first round early enough to keep warm until the second round is complete. Invite your guests in time for the second round. It's best to put your money into what you know you and your family will enjoy w/friends. Don't let your eyes get bigger than your stomach.