Today's question was emailed in:
First I feel that it is important to clarify... NOT EVERY WOMAN IS THE SAME.
There. I felt the need to yell that out to the world.
Because there are women who can finger themselves or play with their nipples, etc. to get themselves off.
I'm not one of them.
I almost exclusively require a vibrator to masturbate*.
It is a combination of my body not being sensitive to my own touches and the time and effort it can take to masturbate. I masturbate more when I'm trying to go to sleep than I do when I'm horny (do people still say horny?).
But honestly, their isn't a "most women" answer because it can vary wildly across every woman. Even the preference of dildo over vibrator would depend on if they penetrate or clit stimulate.
*Or a detachable shower head!