There was certain pragmatism to the choice. Europe faces a much faster phaseout of R-22 than the United States, so manufacturers had to move quickly than their American counterparts. R-407C operates similarly to R-22, so equipment did not have to undergo a major redesign.
But while unit manufacturers dip toward 407C, the major refrigerant manufacturers are taking a neutral position as to what refrigerant will eventually dominate the air conditioning sector.