It's pretty big, second to SDCC I think. I'm not so much talking amount of people big but physically as large (booths/dealers.) I'm not saying SDCC isn't HUGE though.
I guess, thinking back on it, it's not as big as I remember (WWC.) My vission on it is skewed, I went to WWC 1st for years, and compared to any other convention (minus SDCC) it's HUGE. So when I went to SDCC I wasn't blown down by size as much as atmosphere. I remember thinking "this is IT?" cause I imagined SDCC about twice the size it ended up being (causer everyone said WWC was NOTHING compared, BS.) But it's a nice runner up to SDCC if you live in the MW and can't make it out to Cali.
ANOTHER quick observation: SDCC has more stuff crammed in a large space, WWC has a large space too but a little more spread BUT at SDCC think about how many dealer booths are the SAME DAMN THING! Half off trades and old SW figures type. Yeah, WWC has them too but not as many and I think that's another reason I wasn't' as blown down by SDCC (loved it, wanna go again, just not amazed) was that every other dealer was half off trades and bargain "Kingdom Come" toys.