I am looking to book a ticket on AC from PEK via YVR to LGA.

Three terrifc fares that will score me lots of UA PQM (I am *G), but the return flight has a nasty catch. The not so bad catch is a five hour layover at YVR, where I'll be plenty happy in the Maple Leaf lounge (I am pretty sure YVR has a shower, which is really sweet). The really bad catch is I'll arrive at my second stop over about 1 am (when the Maple Leaf Lounge will be closed) to depart on a 6:30 am flight to LGA.

Between YYZ, YOW, or YUL, which airport is the nicest to kill 5 hours or so in the middle of the night? Free (and fast) wifi is a plus outside of the lounge area. They all arrive in LGA around the same time on Jazz flights, so if any of these airports has a slight advantage over the other, please let me know your thoughts.