Martha V.S. Rose, I definitely go for Rose.
I have to admit, she isn't as pretty and smart, but she does love the Doctor. One thing I don't like (I won't use hate, that's a strong word) about Martha is that she always sits and waits for the Doctor to come to her. Rose tries to do things herself, as seen in "The Christmas Invasion" when the Doctor was out cold and she tried to do things 'his way'. This attribute is also seen in 'The Girl in The Fireplace' when the Doctor tells her to stay there but Rose goes to explore with Mickey. Marhta in her position would have stayed and waited.
Some people would interpret these actions as stupid or blundering, but I see these things as acts of bravery and love towards the Doctor. In the last Epidode with Eccleton ('The Parting of the Ways') Rose looks into the heart of the TARDIS just so she could go back to the Doctor. In the end, the Doctor saves her by regenerating himself. He might have done this for martha, but only out of responsibility to get her back to earth. Not love.
I'm not really going to comment on the actors because they don't really have anything to do with the story. I didn't really feel much when the tenth doctor was introduced. I mean who would? After all, David Tennant = eye candy
P.S. BBC has confirmed that Rose will somehow return from the parrallel univers for at least 3 episodes. Billie Piper did sign 3 seasons with Doctor Who and aims to be the first female tme lord.