What would be the category of the employment-based green card? EB1, EB2, EB3, or something else? And are you from India or China? Those factors greatly influence the length of time and complexity of the employment based process.
The employment-based green card has an advantage in that upon approval you directly get a 10-year* green card, whereas you would get a 2-year conditional card for marriage-based followed by another round of paperwork and possibly another interview to extend it to a 10 year card. And employment-based green cards usually don't require an interview, but the interview is mandatory for marriage-based.
The big disadvantage is that if you are in EB2 India/China, or EB3 (any country), or the employment-based process will take years.
*except EB5 investor green cards which initially result in a 2-year card.