Those graph are interesting, but they are just giving a small view of the overall capabilities of each captain.
If you have already played some RPG games, and each of you have surely done it dozen of times ^^ , you know monsters/bosses are always stats stronger than your characters. But you own them every times, because you handle your party better than their, especially about weapons and skills.
Let's take Ken-chan as example.
He is brute strength, with 0 INT, so no spell for Pointy.
All he can do is bash everything, and release special attacks (more bashing
).
Based on his stats, his special attack will do 100 damage at least., like any other STR 100 captain.
But, because of his body stats, he has high endurance, and probably high fatigue as special ability.
When a standard captain can fire 10 special attacks before being exhausted, Zaraki can fire far more (100 ? ^^ ) .
In games, having a character who can fight longer at full strength is more efficient (swordsman) than a very destructive character with little endurance (magician).
In Zaraki's case, he is so endurant he is quite difficult to defeat. Because he will rush at you with full force, and even your strongest attack won't stop him.
And even it does, you will be too exhausted to do it again, as Ken-chan will still ask for more.
Not only he will have enough reiatsu to do it again, but his health is still far higher than yours (ex : Ukitake = 4000 HP/5000 Reiatsu Points - Zaraki = 10 000 HP/10 000 RP
) .
Conclusion :
Those stats are interesting but couldn't reflect the true strength of each captain, as they didn't list special abilities, attacks, weapon tricks, weaknesses, overall HP/SP, etc.
Those graphics are just pure fan service.
(and that's why we ask for more
)