I attended my first full ColossalCon this past weekend (went on Saturday only for the past two years) and I might just have to say that it is quite possibly the best anime convention in the state of Ohio. (Can't speak for MatsuriCon, but I am planning on attending it this year.) A fantastic setting in terms of both location and time of year (The Kalahari in Sandusky at the beginning of the summer) make it a perfect setting for an anime convention.
There were some awesome cosplayers this year (A lot of people doing Attack on Titan and Frozen) but a few stood out; mainly a group of awesome Skyrim guys, three awesome Soulcalibur girls and a few WWE guys as well.
Expect a massive photo dump in the near future, now it's time to prepare for Matsuiri!