I think it comes down to who has the most ‘spare’ time, and by that I mean after you’ve downed tools for the day. So (very generally speaking) for a SAHP who does everything around the house, it would be when the DC are settled, chores done for the day etc. For a working parent, it would be when they’ve logged off/stopped replying to emails.
You look at how much time is left over and split things accordingly.
I’ve always done pretty much everything for Christmas, but this year DH has sourced and collected the main present for his DP, gone to get the tree and put the lights on, collected Ds2’s bike, and ordered a joint for Christmas Eve.
I’ve bought and wrapped all the other gifts for everyone else on his and my side of the family, the dc (including stockings), friends’ Dc etc, decorated the whole house, bought all the crafts and cooking projects for the Dc to do in the run up to Christmas, sorted teacher presents, bought and written and posted all the cards, planned and bought all the food and drink, posted the presents for people we won’t see, dropped off the presents for people who live locally, etc.
I still think I have more leisure time even when all this is done, as I work part time and he works (more than) full time.