It takes more practice to dive with one.
I mostly agree with this.
You can take a complete newbie with a BC, overweight them, tell them to push the small button 'til they float and the big one 'til they sink and they can kind of muddle through with diving. Of course they'll be bumping the bottom, making mini ascents and the last 10' or so of their ascent will be uncontrolled but it will all kind of work.
Being really in control of your buoyancy with a BC or a drysuit however takes much more practice.
Diving without a BC initially requires more finesse. You have to be weighted right and you have to understand how wetsuit compression and tank pressure affects your buoyancy. You also have to be more aware of your breathing as your lungs largely control your buoyancy. You can't just dump an overweighted novice into the water.
In my experience though, you learn that stuff pretty quick and it becomes second nature. After a dozen dives or so with no BC, there's nothing to it. You just swim down, swim around and swim back up. There's no buttons to push or air to vent. If you're a little negative, you compensate by breathing a little deeper and angling your body up a little. If you're too positive, you breathe shallow and angle down. Sometimes you might pick up a rock, scull a little or give yourself an occasional push off the bottom.
The colder the water and the thicker your suit, the more pronounced the buoyancy shift will be. Until November of last year though, I was regularly diving a 7mm wetsuit in 50 degree water with no BC.