Sorry to say it, but you can't make those comparisons. Sure Gaara would win kankorou, but in the end it all comes down to the opponent. Deidara didn't win against gaara due to the fact that he had to protect eveyone, that was just a distractions while he made his real move. Also that fight happened at the place where gaara is best.
As I said Kankorou has other advantages, that can be used better in the field. Besides we haven't seen much from Gaara except failures.
I give them same rating.
What do u mean except failures he only lost to deidara and that was out of technicalities -_- he hasn't lost to anyone else unless u count naruto who really didn't fight gaara Just a pre demon
He won against sasuke (it wouldve counted as a lost if sasuke didn't Persue him)
To me kimmi would've defeated gaara if tht last move would've been made but then again if gaara becomes unconscious (at the time talking) the demon would've killed kimmi
Not counting fillers
Against deidara only lost cuz deidara used village as hostage
Briefly fought sasuke ended no contest
Fought his dad won
Beirfly fought 3rd raikage no contest naruto took over tht battle while gaara went to mizukage
He won against mizukage
Briefly fought muu
Now fighting madara
Now in terms of battling how can u put gaara and kankuro in same boat if they clearly didn't have the same amount of battles or even close gaara in terms of battle and sthregth is below naruto and around sasuke (untill sasuke gets power up to tie with naruto)