Wow, what a huge 'surprise'...
This guy bought an s9i and didn't even notice the difference. S9 (normal) had 14 TH for 1400w, the new one has 14 TH for 1300w. Not a big spike but really not exactly the same.
I actually installed a volt/amp/watt/kwh meter on the 30A outlet I use for my rack. At the wall my 14 TH S9 pulls 1487W and my 14TH S9i pulls 1429W. While my S9i is negligibly more efficient, it's within what I would expect to be the normal variability and a particular S9 could easily be more efficient than a particular S9i.