Salad.
Soup is messy to eat in public. 
I order a salad and ask for Roquefort dressing. If they say, “What?” I go for the soup.
I saw a famous man eating soup.
I say he was lifting a fat broth
Into his mouth with a spoon.
His name was in the newspapers that day
Spelled out in tall black headlines
And thousands of people were talking about him.
When I saw him,
He sat bending his head over a plate
Putting soup in his mouth with a spoon.
– Carl Sandburg
(I always loved this little poem)
Soup, every single time. If it’s not good, I’m not ordering anything else.
But salad bars rarely have fresh produce. I had a salad with dinner last night at one of my favorite dining places, and it was out of this world. I usually eat salads because they’re good for you, but this tasted like everything was just picked hours before. The tomatoes were full of flavor, it had two types of bean pods (string and snap) that were so crispy and sweet. Just wonderful
As for the OP, usually salad. But it depends on the place. There are a few places I eat at that make killer soups, and I’ll go for that. But usually soups are a salt fest, and I prefer to not go down that road.
As you so clearly indicate in your post there are restaurants that offer both. :rolleyes:
In those restaurants I get both. 
I dislike cream soups, so will order the soup only if a non-cream variety is available. If a cream soup is offered, it will be salad for me.
Yes, most restaurants offer both, but you usually get a choice of one or the other.
When did the word “or” become confusing?
I’m seeing a lot of people answering they’ll choose the soup if it’s good, otherwise the salad, but not that they’ll choose the salad if it’s good and otherwise the soup. There’s only a handful of restaurant soups I like, if that many. Anything with bean in it, forget it.
Agreed. I’ve had some that was vaguely fishy-flavored wallpaper paste. Yergh.