Be honest, if you tasted the an IPA with the same grain bill side by side with differing Centennial, Cascade, Simcoe and Amarillo hops could you name which beer had which?
I think the simcoe and anything else would be pretty easy. The last three would be a bit more difficult. amarillo would be the next easiest and I think i could tell centennial apart from cascade.... maybe.
A year or two ago, no way. Now? I'd probably hit all 4. (I differ from the others in being really sensitive to Centennial- I actually think I might be slightly allergic for whatever reason).