Instancing or duplivert

I hope I’m posting in right place. I am creating a ww2 hangar and have duplicated many objects such as the scaffolding on inside of hanger, the dome lights, and many air tanks. So know when I go to rendered mode it just goes black and it looks like it wants to show something but does not. Before that I was getting many fireflies. So I realize I have to much geometry. What are pros and cons to instacing , duplivert,and array. I would like all models to be textured and it does not have to vary. Any help greatly appreciated thnx!

Looks like I have to hit control L to link my object data. I would select the first original model than shift select all duplicate (like 100 lol) then hit control L?

that is the difference between Shift D and Alt D !

happy bl