My first job out of school I got through an online job portal.
My most recent one I got through a headhunter. I’d say that if you get along with the headhunter he/she is very reliable at getting you in the door. I’ve only worked with two headhunters but both of them got me an interview at a specific position that I wanted (whereas if I just blanket applied online I wouldnt’ve gotten either). I do not headhunters would think about entertaining fresh graduate positions though (undergrad). The only downside I found to working with headhunters is that if you’re good they call you a lot. While going through the process I probably got 2 phone calls a week minimum from each.