Hi, Shari! IMHO, there actually are advantages to using dumbbells over barbells in many lifts, primarily upper body lifts, not only because you can quick-grab the ones you want rather than change the plates on the barbell all the time, but also because dumbbells tend to be a little more versatile in terms of what you can do with them. And, with dumbbells your wrists aren't in a constant fixed position that may or may not be comfortable or safe in a specific lift.
That said, I use barbell almost exclusively for my squat and lunge work, as well as bench presses and weighted triceps dips; also for standing bentover barbell row. I do like having both, and I like the barbell much better for leg work than dumbbells; it's easier on the hands, forearms and shoulders.
I would bet that 90% of whatever is "better" between barbell and dumbbells is personal preference. Whatever works best for YOU!
Annette Q. Aquajock