Most likely even cheaper ones are good, but there are differences. Some have sharper/larger spikes, so they can be more effective, but might be too intimidating for those who haven't tried before.

You can affect how strong the effect is.

Put the mat on softer surface so it's not as strong.
Put the mat on a hard surface so it is stronger.

Have a thin shirt on so it's not as strong.
Be topless so it's stronger.