I would save Daisy. In my opinion Peach is a bit annoying and always gets caught constantly. Toad on the other hand is a good guy to save, but I would still go for Daisy just because we never saved her in a mario game ever. Also, it would be nice to see Luigi save her at the end; I think that would be a better ending.
I thought the DS version was a great game, and you have to understand that it's a portable. The console versions have the advantage of tech and visuals, its not like a lot of DS games have good visuals anyways :P