Benchmark balls should be even rolling pieces that you can settle in your comfort zone with. Let's assume you like to play around 2nd arrow, you throw a few shots with your benchmark ball and it comes in light, you would ball up to something like a disturbed. If the shots go thru the face you would ball down to something like the Hyroad Pearl. In your current arsenal I would say the IQ pearl would be the benchmark, although for me that ball was too "flippy" on the back to fit the benchmark category. Depending on the drillings you have on you other stuff and IQ Tour solid would be better. My arsenal goes like this:
Mastermind
Meanstreak Beatdown (benchmark)
Melee (2000 surface)
Melee (oob shiny)
Ringer
Strike King