I've played both courses and in my opinion the Lakes Course at Primm is Shadow Creek - Lite. When Primm just opened, condition-wise it was excellent -- now the conditions are not so great when compared to before. Architecturally, there are many similarities, but I clearly felt that Fazio created more subtleties and spent more time on the "environment" and shot values of every hole. In addition, Shadow Creek has quite a few more striking features or difficult shots. Primm is clearly built with a 15-handicap resort person in mind, while Shadow Creek, while very playable for all, has a few more demanding shots.
Drawing a parallel to food, if you eat at L'Atalier de Joel Robuchon, you are getting a similar meal to what you would get at Joel Robuchon, but a lot of the fineness and subtle flavors you can only get at the main restaurant. Primm Lakes is like L'Atalier.
In terms of price, both L'Atalier and Primm Lakes may be far better values, but I'd be hard-pressed to find anyone who has played both or eaten at both to say that if money were no object, they wouldn't choose Shadow Creek or Joel Robuchon. That being said I play at Primm far more than I do at Shadow Creek!