Anker conversion efficiency (+ discount)

When searching for the ideal powerbank I bumped into this rather big discount: https://www.anker.com/deals/prime_day

Is there a list with the output efficiency of last 2 generation powerbanks.
I’m especially interested knowing this for the:

- PowerCore 26800

- PowerCore+ 26800

  • PowerCore II 20000

In a review on Amazon someone mentioned that the PowerCore II possibly has a lower conversion efficiency.
Of course just after I found that nice discount…