White Noise vs Sound Machines

[mable]

I've noticed that there are two different sound devices.  Some that produce "white noise" and others that have different natural sounds (for example rain or ocean sounds).  Is it just a matter of personal preference, or do different sounds actually work better on for different individuals?

[SleepySam]

I think personal preference more than anything.  A lot of people can't stand any noise what so ever in their sleeping room.  I know that I can't have any light or it effects my sleep.