See, this is like a prisoners' dilemma kinda.
Two premades are at end of game screen. If they both honor each other, they each get great satisfaction. If one of them only honors their premade, one team goes with bupkis. If they both honor their own premade, then at least each premade gets honor.
The analytical person should notice that this can be broken down to (in terms of net honor gain)
Both honor other premade: +1 each.
One honors other premade, other honors own premade: +2 one, 0 the other
Both honor own premade: +1 each.
Considering there is no way to predict nor guarantee who other players will honor, or if they will honor at all, statistically speaking in a 4 man group where 2 teams of 2 premades exist, the best way to guarantee everyone walks out with something is to honor your own premade (either end up with +1 if other team does the same, or +2 if the other team honors you as well).
Statistically speaking, honoring your own premade would be worth it.. Iff (if and only if) the honor for premades counted the same. Riot has stated that honoring premades frequently would not count as much as honor from random people. Thus, to be honest, statistically it's up in the air what's more effective.
The right thing to do, however, is to honor whoever you think deserves it most, regardless of premade or not.