It really is a function of how often you fly and perhaps your age/health and what condition you need to be when you get to where you are going (e.g. can you take a day off to recover).

If you are doing three international flights a year for work, economy class is fine (I can catch up on movies). If you are doing them once a month, economy all the time can easily become rage inducing. Business class at that point becomes a matter of whether you retain that employee (who you need to travel a lot) or not.