I actually flew in economy twice after repeated trips in J YVR-HKG and I survived! It really wasn't that bad. All what your head space is in. It is a long trip so the service and the extra room in J are appreciated but not essential to one's survival. I would opt for the YYZ-HKG nonstop. As the 777s come on board that will be the way to do it (on AC)!
I would do 777 in any seat in econo, but preferably bulkhead.