Chambudzi
Following your reasoning, the 787 should have a single engine type. I'm not disputing that the 777-300ER is now picking up orders. What I said is that it would have picked up more orders more quickly if it had an engine choice. Also, most airlines would tell you that the competition between engine manufacturers delivers lower prices.
747FOCAL
Don't dispute valuation differential - historically - bit different now. SAA operate both 524H-Ts and CF6-80 powered 744s - ask them which they prefer. Cargolux switched from GE to RR and CR2 will probably tell you how they're getting on too.