Nobody cares about gambit to begin with, the triple infamy weeks do nothing to make people want to play such and unenjoyable game mode. Double exp gains for a week would be so much more useful and fun to the general player base.
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Infamy is a source of powerful drops as well as new armor in beyond light. Double exp is really only useful if you haven't completed the season pass or want to farm eververse engrams. Both offer little value if your max light and finish the pass. I'd rather have double infamy over exp as this means new weapon rolls. Also bungie may add things like ascendant shards to valor/infamy resets in beyond light.