It depends on the circumstances although I think stranger rapes are generally worse than "date-rapes". First of all, if a woman is on a date with someone, chances are that she is at least somewhat interested in that person, not necessarily for sex, but at least interested in some way. This is opposed to a woman being raped by a stranger that she doesn't know, and has no interest in. Stranger or forced rapes are generally more violent than date rapes. Some stranger rapes, the woman is assaulted with a weapon, or is intimidated by a group of men with the rapist, which is a much more fearful and violent rape. Date-rape can be just as violent, but generally it is not as violent as stranger rapes, especially when weapons are used. Women who have been date-raped, have at least done something that led to the rape. But for trusting a man into her house, but for getting drunk with him, but for trusting him, but for acting flirtatious, but for teasing him, but for many other things. That's not to say that she deserves it or "brought it on herself" G-d forbid, but her actions lead more to the rape than in most cases of stranger rape like if a girl gets nabbed off the street and raped.
In some "date-rape" cases, the actions that a woman does that leads to the rape are even partially culpable, like getting really wasted with a guy she just met, doing drugs with someone, allowing him to go back to your house, going out with a man very late at night, showing up to a man's hotel room at 2 am dressed scantily (like the date rape case of Mike Tyson).
I think in general, stranger rapes are more terrifying and permanently damaging to the rape victim than date-rapes are, and I think rape victims themselves would agree with this.
I would be willing to bet that if you could get a woman comfortable enough to talk about her "date-rape" she would probably say that it wasn't as bad as if she was raped by a complete stranger in a violent and threatening fashion, and that she thinks that stranger rapes are worse.
Much of the time with stranger rapes, the woman is literally fearful for her life, she doens't know if the man is planning on killing her since stranger rapes are so often associated with murder. On the other hand, date-rapes are not as frequently associated with murder, and although the women might be fearful for their safety or harm, they usually do not have an apprehension of death that is associated with rapes by a stranger.
Of course rape is rape, but that doesn't mean that all rapes are equally as damaging or terrifying to the victims.