A minor factor in favor of the IAH/MUC flight is that there are several Western cities where there are nonstop flights to IAH (versus ORD). These include SJC, RNO, ONT, ELP, TUS. Add nearby regional flights and Mexico flights, IAH becomes a more significant hub, which may justify flights to both FRA and MUC.

I've taken the IAH/MUC a couple of times this year and much prefer MUC to FRA. Unfortunately, they are still expanding MUC so I've had to take a bus from the airport to the terminal. Of course, this happens at FRA too.