Okay, so this year I went to both GenCon and Origins. I'd always wanted to do both in a summer, but could never afford to. This year, I still couldn't afford to, but I did anyway. I figured I was now in a good position to compare the two cons.
Attendance
GenCon has more people...I don't know exact numbers for this year, but in past years GenCon has had two to three times as many people. That was actually a downside for GenCon, given the space they're using.
Facilities
GenCon is held at the Indiana Convention Center in Indianapolis, and Origins is at the Columbus Convention Center in Columbus Ohio. The Indiana Convention Center is far too small for the size of the con, meaning that most of the con happens at half a dozen hotel spaces around the convention center. Lots of walking!
The Columbus Convention center is a larger space, and so more of Origins fits inside it. There are still a few things that happen in adjoining hotels, but not nearly as much as at GenCon. But, there's still lots of walking since the convention center is larger.
Event Availability
GenCon had more events (at least of the sorts I was interested in), but not enough to make up for the extra attendance. It was very hard at GenCon to get into certain events on generic tickets. At Origins that's generally easier.
Dealer's Room
I liked that GenCon had the art show and the dealer's room combined. Made for a nice seamless browsing experience. On the other hand, the GenCon dealer's room was way too small for the number of people crammed in to it. Origins didn't seem as crowded.
Overall
Overall, I found that I preferred Origins. GenCon did have more LARPs, which is a favorite of mine for conventions.
