To me, brawl is primarlily about:
mobility
recovery
safety
attack opportunity/punishment
in brawl nowadays, i put a high priority on being able to not get gimped/ recovery, and even though things can get worked around, a limited recovery like Ike's is something that when i look at the high tiers is the biggest problem.
for example, i compare Sonic vs DDD to Ike vs DDD, and thought about how much easier it is for DDD to do certain things, like bair you off the stage and keep you off ftw. I gave that situation to sonic. Then i thought about who has a better chance to avoid stupid things like chaingrabs, and again i give it to sonic, since only a frame perfect one will keep him in the CG.
though ike is more powerful, it doesn't mean he will kill faster than sonic. also, punishement is very important and i feel that against chracters like Meta, D3, and falco, he has an even harder time punishing than sonic, and at the same time, lack the mobility they do to survive if caught in horrible situations. Out side of jab, i dont really see what reliable move he has to get people off of him.
Compared to sonic, his jab isn't as good as ikes, but i've seen it still used oos, and he has more common oos options, in addition his mobility is superior to ike, so the possibility of being put in horrible situations is lower.
Ike can use his moves best it seems when opponents are trying to get back on stage, but that level of pressure can exist with sonic all across the stage, so i think sonic is better at controlling the field against more chracters.
to me, the fact that he can get killed in more ways than sonic and that his powerful offense doesn't deter that weakness enough, gives sonic the edge in a tourney setting, even thought the matchup between sonic and ike is close to even, and IMO, only because of sonic's lack of KO moves compared to Ike, which as you can see, still isn't enough to give Ike a more favorablt matchup against someone like Sonic.
tha'ts all i got...