I have 3 dc (now adults) and staying at home it varies. Sometimes having all three when they're working together is easier than having to entertain one. But going out:
Any two are easier than all 3.
Any one is easier than any pair.
But that's simply on the fact that it's easier to do what one person wants than consider all three. I suspect if I had three close friends, much as I would enjoy hanging out with all three if we were just sitting round that would be great. Going out, I suspect I'd say the same as above.
For example with the dc. We go to a theme park. Dc1 wants to go on her favourite ride which dc2 and dc3 are too small to go on. Dc2 would rather go and look at the expedition which the other two think is boring, and dc3 loves another ride, which they can all go on together but the older ones feel it's a bit beneath them.
Dc3 will go in the buggy if needed, dc2 will get tired, but can't go in the buggy and will get moany if there's too much walking at the end. Dc1 tends to put themselves at the bottom of the pile if they negotiate between themselves and then get upset later that they didn't do their favourites. Dc2 can be a bit of a bolter, so if they see what they want may go straight off without thinking, so I need to keep an eye on them. Dc3 needs a sleep otherwise they will sleep on the way home and be up to midnight and won't sleep if we don't have a pause at the right time etc. All things that have to be considered with three.
If I only have one, it's simple - I do what that one wants within reasons. We eat when they're hungry, stop if they need a rest and leave when they've had enough.
With two I have a little negotiation, but it's fairly easy, we do one then the other. Not too much waiting around and maybe I use a little bribery with the one who's going second.
With three it's harder. Do we do dc1's thing first because the queue will be longer if we wait, or do we do something they all like first? Dc3 is the worst at queueing (naturally) so do we reduce the inevitable ragged temper from them by doing more of their favourite rides which have smaller queues. etc.
It's simple practicalities that you need to be on top of with more than one. But, yes, I'm glad I had three. They all have times when they get on better than others, but it is nice when they're all working together, and it happens more often than you expect.