Personally all of the items can be good but it is more in the sequencing and use of the canvas (yard) for me. I use a lot of trees minis, med, mega and spiral but I also use existing structures like trees and playground to add to them. My kids' playgroung has an elevated deck and a firepole so the pole becomes a mega tree, the deck an elf workshop, their slide a water fall down to an ice pond and skating snowman. My roofline will look like a gingerbread house with C9 gumdrops. The other elements just add more icing. I don't use any blow moilds or other things. Although this year I am gonna add a projector for snowflakes on the house too.
Again, I think the sequencing is what makes the wow factor.