One doesn't have to dance silver material in a silver competitive event. I can think of at least one local couple that has been winning or placing in silver and gold events with only bronze material. They keep it simple and maintain a nice frame, while many of their competitors are breaking frame to get into wing. On the other hand, silver opens up some good options. For example, silver quickstep figures like V6 and Quick Open Reverse allow you to use the center of the floor, unlike the bronze figures which pretty much keep you hugging the sides of the floor. Silver waltz allows you to use the Progressive Chasse to Right/Outside Change combination and Weave from Promenade, both of which flow better than the bronze Basic Weave, and especially Natural/Reverse turns and Closed Changes.
I think you should almost always be working on fundamentals. But sometimes, it can be worth it to divert attention to new figures. I think it would depend on:
-How much you already have of the fundamentals needed to support the new figure
-How much time/effort you would need to invest in the new figure
-How much the new figure could show you to better advantage