Do your research about the airline and the particular aircraft that is used for the flight and check if good seats are still available. Seatguru will help you to see if the seats offered are ok:
http://www.seatguru.com/
Most international flag carriers have a very good business class. Air Canada has for sure and the difference to First is not that big to justify the price difference. Most US carriers are crappy in both First and Business. I would go with their premium economy and try to purchase an upgrade for 500 bucks each way, as long as they have available seats. Their full price F and C fares are way to expensive.
Some top airlines offer additional services for First Class passengers that are a nice bonus. They pick you up from home with a Porsche Cayenne and drive you right to the airport with VIP security check with no lines to wait in. Some provide a butler to guide you through airports and who take care or your luggage, etc. It's very convenient.