If you ever have the chance, you should upgrade your seating to business or first class. It is much more comfortable with better options for food and drink as well as have more room for your legs. Most of the time, you will see both business and first class on international flights and not domestic flights. On domestic flights, they may have one or the other, but not both. To compare both of these is quite simple.
First class costs more and is a little bit better than business class. There are many more perks for the first class than business class. When they call for your flight at the gate at the airport, they will seat the first class passengers first and then the business class.