For me, I get the best burn on the pec deck. If I didn't have that machine, I'd go with incline & decline (and flat) dumbell flys. Barbell press is great, but for me, it doesn't isolate the pecs as well as flys, and my delts & triceps will exhaust before the pecs do, so I can't get my pecs to exhaustion with the barbell. Barbell bench pressing is also in my routine, but if I have to cut a workout short, I'll give up the bench but do the pec deck that day.
Charles