Tough choice, but the damage bonus on the two single swords is 28% each so I think those are slightly better for that reason.
Her STR bonus is 7 though so the STR bonus to two handed isn't too shabby. And it's not difficult to have the two hander negate all armor since we have lots of armor shreds in the party....
hmm....

This game has more fun itemization than a lot of games I've played.