For BEST performance for the CPU alone, using the IWC as an intake makes perfect sense- but it ignores the rest of the system. If you have positive pressure generated by fans elsewhere in the system, you can easily get away with the IWC oriented as an exhaust, because it will effectively be the same- or better, really- as having it as an intake.
I think Corsair's instructions, like Nvidia's of having 600W per GPU, are 'default to worst case'-style. If you have an average case and added no additional fans, you might have one intake and one exhaust- so making the H110i an intake makes sense. But if you have significant amounts of intake, like you should, then setting it to exhaust actually makes more sense and will net higher performance.
Canon 6D||[24-105/4L IS USM|100/2.8L Macro IS USM|70-300/4-5.6 IS USM|40/2.8 STM|50/1.4 USM|85/1.8 USM|Samyang/Bower 14/2.8 Full-Manual Rectilinear Wide-angle|
Canon EOS-M|11-22/4-5.6 IS STM|22/2 STM|EF-M 18-55/3.5-5.6 IS STM|
For sale!|24/2.8 IS USM|