If we are at home in our own house, we generally manage to get "down home" during December for a weekend and visit both. And we will always manage to visit over the Christmas break - we go to DP's for NYE (there's a big family gathering) and visit DSIL's family en route (they're about 30km apart, almost 280 km from our house), and then go a further 200km to DMIL and DBIL's family, before completing the (slightly circular) journey 270km home again. That's usually a 2-4 day trip, depending on what else is going on.
On years that we go "down home", we rent a cottage in the locality. As DPs and DMIL are 20 km apart and both want every moment they can get, give us guilt trips about spending too much time in the other house, and we get no peace at all if we don't have an independent base. So, all the (very few available) rentals require payment for a full week for Christmas, we usually stay for most of the week if not all.
We spend time in both houses around the day, (in fact, we have sometimes driven down the 2 cars for this trip to get around and allow us to split time better across the 2 houses and get other things done also!).
And on the day, we get up, have breakfast, go to mass. Then into DMILs in mid-morning for turkey lunch, presents, etc, for about 4-5 hours. Then on to DPs in late afternoon for another 4-5 hours doing presents, turkey dinner and then waddle back to the cottage to groan at our full bellies and sleep.
Boxing Day is DD's birthday, so we always host a gathering and any of either family who are available come along - if we are in our own house, there may occasionally be 1 or 2 people up, if we are "down home" there can be up to 25 over the course of the day (if it's a year that everyone is "home") - but not usually all at the same time as there are other extended family gatherings that day that some need to juggle around.
I'd really love a year when someone actually comes to us for Christmas, or at least, doesn't give us a guilt trip if we decide to stay put and suit ourselves. Because we are always really busy, between FT work (including international travel for both DH and I), dealing with DD's SN's (ASD/ADHD - high functioning but still lots of problems that need managing), and extra-curricular activities (mostly to support DD but we've become sucked into the organisation of them as "people who are willing") - we literally don't have any mornings to sit at home with the papers or just do nothing, so Christmas Day is a very very precious day of doing nothing and no expectations.....on the years we manage to stay at home at least. (Well, we still have mass and a couple of visits to make, but it is a slower paced day that starts much later than normal - even Christmas Eve means having to be in work by 9am!).