A centre pair is possible on both to be closest together. The 777 F cabin is more spacious, though as mentioned the novelty of the nose of the 747 is attractive to some, and will become less common as the 747 fleet is wound down over the next 5-7 years. 1A/K on the 747 requires higher status to reserve, it is held for BA Gold members, and I presume OWE also, but not 100% about that.

Note that window/aisle combinations on the 777 are not properly adjacent, the seats are offset, to be right next to each other you need a centre pair.

Either way, enjoy.