Well it depends.
Rei is more like "Im not aware that im a woman so i go around naked in front on man and i dont mind having sex". And she must be very submissive in bed accepting any strange suggestion you might make.
And Asuka is like "You fucking bastard you are ugly, but you know what?, i will punish myself and have sex with you. (after sex) oh for fuck sake you fukc like a girl, i'll show you how its done (more hard angry sex). I hate you, good night"
So it depends on what you like the most. Tsundere or "mech like" girl.