alt Hacker NewsOK. I think my opinion and definition on "easier" is indeed vague. For "easier", I'm only comparing the thinking difficulty.
Yes, medal is function of ranking but not difficulty.
Nonetheless, I would say that IOI more focus on thinking, which I to some degree is not that good at, while ICPC is more like a mix thinking and implementing. Therefore, my ability to implement stuff can improve my ICPC ranking but not IOI.
As a former ICPC winner, I'd say ICPC is mainly a test of teamwork, given the format of the competition (3 team mates, one computer, scoring that rewards clean solutions submitted quicker, tackled in the optimal order for your three sets of skills, etc).
Sure, you need to be individually good at thinking, etc. But the difference between 1st and places further down the ranking is teamwork.