Hello and welcome to Flyertalk, dsed.
Personally, I would be tempted to de-select the least convenient options as opposed to looking for the "one best way".
First of all, don't be tempted to choose Alitalia, even though their routings will probably seem the most convenient. Their business class product is below average, and there are serious questions about the viability of the airline.
I would would also avoid BA because you have to change planes at LHR, the least reliable major airport in Europe, KLM as there effectively is no business class for the intra-Europe legs, as well as any connections within the USA because of the customs re-screening thing.
That essentially leaves you with AF, IB, LH/LX and OS. My understanding is that the product ("lieflat" seats) and service (average to great, depending on the crew you get) is similar, so I'd decide based on the best combination of schedule/pricing I could get from any of these carriers. These things being equal/similar, I'd be inclined to go with a carrier that belongs to my preferred alliance.