Difference Start/Turn Off/Standby VS Power Options Standby

If wrong groups please advise.

Is there any difference between going to sleep via method A and B
(below):

Method A: Start/Turn Off Computer/Standby
Method B: Control Panel/Power Options/Standby (Ex: Standby after 15
minutes)

The reason I ask is that I am having trouble w/ USB Flash drives.
Using method A and waiting a while before waking up causes the drive
to be unavailable until unplug and replug it in. It is visible in
Explorer but you can't read/write to it.

Using method B: The drives seem to work OK the next morning.

The drives are plugged in to a powered USB hub.
Win XP sp2

Thanks