I've been attending since 2006, and the Vancouver Hilton in 2007 was definitely my favorite venue. It was both horizontally spacious and provided with an abundance of open scenery outside of the hotel. Being literally across the street from a considerably large park, with water features and monuments, just provides so perfectly for cosplay photo shoots and meet-ups, or just for hanging out. It was very nice to have lots of "wandering room", as it were, and I think the Vancouver Hilton definitely offered the best in this area, of all Kumoricon's venues.
It also was not a very tall hotel, which was great as elevators never took a cruelly long time to arrive anywhere.
Really, Vancouver Hilton just has it going on, and I'm so happy to know we're returning there next!