Large helicopters are not as difficult to fly as small ones, simply because the time constant of their instability is longer. This is similar to how it is easier to balance a broom on the tip of your finger than a pencil, and a pencil is in turn easier than a toothpick.
I keep trying to explain this to my friends in the aquarium and terrarium hobbies.
"I want to build a tiny one. It'll be so cute."
"It's going to crash in 30 seconds if you so much as look at it funny."