If you have a toy, it would be good to compare with. It depends on how sensitive you are. The average user should be able to enjoy 3 Vrooms. 4 Vrooms is ideal to have more of a choice in power. 5 Vrooms is for power queens and more sensitive people can't stand something that intense.
I recommend buying a toy that is 4 Vrooms but had graduating settings. That will let you know what you prefer.