DF aside, Lucci's Doriki was almost twice as high as Kaku's. Even if the Giraffe was stronger, that wouldn't make up for such a large difference in the first place. It would mean the Doriki boost of the Giraffe fruit is 2000 Doriki above the Doriki Lucci's fruit would give, which isn't the case.
And while the Giraffe is stronger in full Zoan form, in terms of Hybrid it doesn't really matter, since in Hybrid Lucci can turn into a bulky 5 meter tall human-leopard hybrid, while Kaku's hybrid is mostly just Zoan on two legs. On top of a carnivorous Zoan giving Lucci more bloodlust.
Rangyaku? Lucci's wasn't far off, given how he destroyed the tower they were in completely with one Rankyaku. Shigan? I don't see how the Giraffe's dull claws benefit Kaku's shigan (which he apparently didn't even use against Zoro), while Lucci's Zoan gives him sharp claws, allowing him to thrust through bodies with ease:
With Lucci using different advanced forms of Shigan, even a long range one against Luffy, I don't see why you would give Kaku the upper hand.
As for Tekkai, both used it, Kaku used it too on his neck and when protecting himself from his own Rankyaku rain. Lucci's Tekkai is superior. He even showed advanced variants of it, like returning the force of the attack dealt to him.
And obviously, Rokuougan also depends on Doriki, which is just your overall power level. So with a highr Doriki, the damage output will be even higher. Interestingly enough, Lucci said that Rokuougan is accessible to those who mastered the 6 other arts "to the extreme". So in this context, you may argue that Kaku slightly excelled in Rangyaku due to it being his proficiency, while Lucci outclassed Kaku in the rest.