Sory for kinda necroing it, butnobody suggested to dump both girls. Yes, it could end up in two suicides and limp dick, but!

If he would choose one of them, the other one would feel betrayed (not without a reason!), humiliated and worthless. She could kill herself, if she have depression or other shit.

But if he would explain the situation to both of them, apologised and step out from their lives, there would be 3 (or 2, not sure about OP) broken hearts, but it would be much less painful and degrading, than being the worse one. Also how would the other girl feel as a reason for someone's suicide?

I think that could be the safest solution.

Or choose the prettier girl and f the other one.
jk