Garp should spank on Akainu mid-high diff. He's already implied himself to be capable of doing so, should be on par with an old unscathed/non-sick WB, who would shit on Akainu, and evidently has far more Haki power as shown against Marco.
Out of the 10 comments, it's split right down the middle. Damn.
I guess I lean towards Garp and his hype partly because of what Apex said. I think Garp might have been overestimating himself a little bit but he was pretty confident nonetheless. I think Garp's CoA would allow him to take attacks from Akainu to the point where he's like a tank. We know that Akainu probably won't last long taking real hits from Garp, it'll probably take 3-4 to put Akainu down for the count. Akainu can use his magma to keep some range on Garp but I honestly think Garp wouldn't care and would go for the attack and take some damage if it means putting down Akainu.