On flights over 8 hours, business class transforms the experience - lie-flat seats, lounge access, better sleep. On short hops (under 4 hours), the premium buys you little. A common approach: business class on long-haul legs, economy on the short ones.
This is a personal call that depends on your budget, your priorities, and how long your flights are.
The case for business class is strongest on long-haul segments of 10 hours or more. A 14-hour flight from Los Angeles to Sydney in economy is survivable but exhausting. The same flight in business class, with a lie-flat seat, proper food, lounge access, and space to actually sleep, means you arrive in Sydney ready to explore instead of needing a recovery day. Multiply that across 3 or 4 long-haul flights and the difference in trip quality is significant.
The case against: the money you spend upgrading to business class could fund weeks of ground travel. The difference between economy and business on a 6-stop RTW trip might be $5,000 to $12,000 per person. That's a safari in Tanzania, a month in Southeast Asia, or a week in a Santorini villa.
The hybrid approach is what most experienced RTW travelers choose. Business class on the 2 or 3 longest flights (transpacific, transatlantic, or anything over 10 hours), and economy on the shorter regional hops (3 to 6 hours) where the premium cabin barely matters. AirTreks builds mixed-cabin itineraries as a standard practice.
A few things worth knowing. Business class pricing varies enormously by airline and route. Business class from the US to Asia on a major carrier might be $4,000 to $6,000 one-way. The same class on a Gulf carrier (Emirates, Qatar, Etihad) routed through their hub can be substantially less. Your consultant knows where the value is.
Premium economy is an underrated middle option. Wider seats, more legroom, and better food at roughly 50 to 70 percent of the business class price. Not every airline offers it, but when available, it's a solid compromise on those marathon flights.