Originally Posted by
smachiz
they are often synonymous for "domestic" flights, but for international, there's a big difference in the soft product (you'll get better champagne, caviar on most airlines, more meal courses, and better ground service/lounge). The hard product varies from incrementally better to dramatically better (in terms of seat space, comfort and type), but in general, you can expect lie-flat beds in either class of service across the pond.
For your purposes, business class ought to be good enough.
What is a "reasonable" amount of money for you to spend to get there in business class? and how many miles do you have and in which programs?
Not true in all cases. Some airlines, IIRC AA and UA, still offer both FC and business class on some domestic flights such as nonstop coast-to-coast.
However, AFAIK Air Canada only offers business class internationally, not FC, and has no genuine three-cabin domestic flights either, although I'm not sure what they do about premium economy or economy plus currently.