Real hair is definitely best but real expensive and you wouldn't want to use them hard. I have a few wigs and they are certainly good enough. They also make a great target to cum on since you wouldn't mind ruining them because they're cheap.
I have bought many inexpensive ponytails and tied them together to make a thick ponytail. Even synthetics are good for this!
If you can afford real hair ponytails, use them gently!