I’d choose 5K out and 5A back.

Reasons below:

Expertflyer shows 12A/K blocked on B78X. This suggests bassinets in the rear CW cabin which may be bothersome for you.

The daytime outbound will have the sun on the A side and and the reverse on the way home.

Also, looking the the window layout on Propero’s seat map, row 5 looks to be one of a few rows in the front cabin with 2 full windows in decent places (rows 7 & 8 are the others).

I’d avoid row 6 at all costs, window layout suggests a fuselage join here which likely accounts for the missing window.