one leaves no room for doubts as far as eroticism is concerned.
Her genitals fully exposed promote ultimate sight for him.
On the other hand, the open position isn't much to look
at in terms of deep penetrative angle of sex. As her thighs
in tight geometric angle will limit clitoral stimulation.
position stems from the one whose lovers lie with outstretched
legs, and only then she bend hers, lifting them up she allows
penetration. If legs feel rather cumbersome during act she
may move on to another variation.