I haven't tried the Backstage so can only base my comparison against the original Diorshow and Diorshow iconic. I loved Diorshow, didn't think I could ever find a better mascara but I was given the Iconic as a gift and it's even better. I prefer the Iconic brush and the definition you get with the mascara is amazing! My eyelashes are naturally quite thick and curly but they are short, so what I need is length and the iconic lengthens my eyelashes even more than the original and as also with the original, doesn't clump.
I would definitely recommend the Iconic, it's a great mascara!