I have to add my 2 cents here. A large penis can hurt and do damage.
I have been married twice. My first husband was average (6) and it was all good. Then along came my second husband, he is not average, he is huge huge huge (11) and we have been married 7 yrs. and during this time he has hurt me numerous times. To the point of OBGYN visits and getting stitches....ouch!
For the initial question of whether or not size matters. I say yes. It does. There is not a better turn on than seeing a nice size 11 penis coming your way.
Also, my first marriage- I never had an orgasm during sex. He always had to go down on me with his tongue to achieve an orgasm. The second husband-well, I now have multiple orgasms during sex....I think it is because he can reach my 'G" spot.
So yes, for me, size matters.