Why does Rufus like both Dana and Alice in "Kindred"?

Well, on the level of plot and symbolism, Rufus likes them both because they are related. This gives Dana a direct stake in what's happening in her past (rather than just being a sort of confused spectator).  Physically, they look similar, so it is fair to say that Rufus has a type. 

On a deeper emotional level, he likes both of them for some of the same reasons he gets angry at them at times: because there is something deep in their hearts and minds that challenges him, that makes him want to be, in the words of a contemporary movie, a better man, and something that he wants to conquer and possess.