Two kids is hard at the start, but now that one is basically 1 year old, I realized my older one is doing all the work I was doing with her. That is, the favorite toy of the younger kid is the sibling, not the daddy. Spares the boring part (repetitive boring play), gives more time for instructive play.
3 years old is a full time thing, but there are things that are quite fun to do together. We play videogames, board games, or I just let her climb on me and enjoy that.
Also going to the pool together is really nice and they get exhausted.
Sometimes you TAKE your free time. Kids are bored and want to play with you, but you haven't had time for yourself in 5 days, you just take it, even if they want to play with you. They will get bored, but more often they will figure out something to play together.
Overall, pretty happy, when they are both 3+ we can play a whole bunch of things together that I'm looking forward to!
I can't tell how it would be with just one, but there are tradeoffs to both sides.
We don't use much daycare, our 3 years old goes to school 4 days a week for 3 hours only (purpose was learning, not babysitting).