Well...I've only had one cock in the last 20 yrs, it's a little above average in length and girth and it suits me perfectly.
Any other experience I've had has been with toys and I've got different lengths and widths, they all have their benefits. I do have the problem though with length that if it's too long, it will hurt when it hits up deep inside me...hubby usually can't go balls deep into me unless I'm in one certain position and I usually don't go very deep when I masturbate. We also had a dildo that was too wide for me...it just filled me up too much and I couldn't orgasam, but it was a really big one IMO...we don't have it anymore. LOL
Most of my favorite toys are on the smaller side, but most of my orgasams are triggered by my g-spot so maybe that's why I prefer those. Some women's orgasams are triggered from deeper penetration, those orgasams are sometimes referred to as cul-de-sac orgasams.
For me, I think it's less about overall girth or length, but it's more about having a good thick head...nothing like a nicely formed mushroom shaped head. Mmmmmmm!