I think KO has way more upside than Giannis.
I actually think Giannis might be a tad bit overrated by everyone, but that dude just turned 21 years old. Olynyk is turning 25 in a few months. I don't think it's realistic to say Olynyk has more upside.
I do like Olynyk, though. I'd love to see what he could do with 30+ minutes every night.