For me it is purely physical, rather than the mothering/"I will take care of you" vibe.
Younger women are amazing, but I don't know why but older women's faces and imperfect bodies just drive me crazy.
I loved Miko Lee and Mika Tan. I even liked Mika Tan now where she has gotten a bit chubby, but she doesn't seem to be so active recently which is a shame.
As a MILF / GILF lover, I have too many favorites but Yumi Kazama, Honami Takasaka, Chisato Souda, Haruka Yamamoto, Chiyoko Kawabata, Tsubasa Fukayuki are a few that come to mind.