"I saw him going" vs "I saw him go".

Which one of above is correct and why?

Somewhere in a book,I saw this line - "I saw him go" which I find stilted because I feel notion for line "I saw him going".

On little dwelling,I found that this is case of incomplete predication and an infinite "go" is used as objective complement.

I don't found anywhere mentioned that a gerund can be used as objective complement(instead I only found that gerund can be used as subjective complement).This confused me whether "I saw him going" is correct line or not.

Tell whether line with gerund is correct or not.If yes,which of the two lines is preferable in different situations and why?