I agree about the salt in soup - and just about everything else, but it isn't a restaurant thing alone, take a look at the list of ingredients in a commercial soup some time.
My first choice will be soup, but only because I have no desire to consume another standard 'filler' salad made from the same old boring stuff and using the same old bottled dressings in many cases (although last time I asked for some separate oil and vinegar to do my own, I got rancid oil, so...).
If the soup is one that doesn't appeal to me, then I go on to the salad, and if it is a 'standard' one I pass on a first course completely.
I must say that I rarely dine in a restaurant where this question would be asked.