The left one is EB only. The right one was on the XLT and Limited.
I think they are the same - according to the 2008 Explorer brochure:
Grille — Chrome, 4-bar design (listed as standard on XLT and Limited)
Grille — Chrome, 3-bar design with nostrils (listed as standard on the EB)
Each is listed as unavailable on the other.
I didn't quickly find a 2006 or 7 brochure but I can't see why they would change the grill design within a generation.