Not necessarily
 
For single deck and double deck I think that HiLo performs a bit better.  
 
According http://www.bjstats.com/bjre.asp here are some comparisons in SCOREs between KO Preferred and HiLo+I18. 
 
 
                            KO    HiLo 
1D,H17,26 card cut(1-4)    34.98 33.07 
1D,H17,21 card cut(1-4)    73.25 69.65 
 
2D,H17,DS, 43 cut (1-8)    36.73 33.81 
2D,H17,DS, 35 cut (1-8)    50.95 47.66
 
 
As you see, KO is slightly better for some very common 1D and 2D games. 
 
I personally prefer KO over HiLo in single and double deck because with HiLo I would have to perfrom a TC conversion on almost every hand. In 6 deck, the TC changes less often and so I prefer HiLo.