I would keep my own room as a foothold up to the last possible moment, until I found out that they had suitable room for me (not stuffing 9 people into every inch on the floor), then cancel my own and switch over to theirs to save money that could be applied to other con-related use.
(something I plan on doing next year)
WWYD if you had no money for a room at all and had to choose between leaving the con at 11 PM, an hour after the rave started, to catch the last bus that you could take home, and staying all night long to catch the next bus at 5 AM, enduring lack of sleep, and cold? Also the bus stop is on the other side of the river, across a long freeway bridge.