Except for small differences in seat pitch the Y product is basically identical aboard of both. The A330 is a bit quieter, so it has a slight advantage. However if you have no status with *A, I'd suggest to fly the 763, as it has only one middle seat per row. So my choice would be 763 via MUC
If select the 763 and you're going after a window seat, beware of the windowless seats in the small Y cabin.
310, 319, 320, 321, 333, 343, 345, 346, 732, 735, 73G, 738, 744, 752, 762, 763, 77L, 77W, 788, AT4, AT7, BEH, CR2, CRA, CR9, DH1, DH3, DH4, E75, E90, E95, F28, F50, F100, Saab 340, YAK40