Snow White and the Huntsman has some decent ideas in its creature designs, but those are unfortunately ruined by terrible CGI instead of practical effects (Terry Gilliam in his prime would have been a great fit). And the plot is a disaster, never developing any of its characters. More than anything, the disaster is Kristen Stewart's dead fish performance, a contender for most lifeless cinematic acting of all time.
Aside from the amazing costumes and somewhat fun lead performances, Mirror Mirror pretty much blows.
Snow White and the Huntsman, on the contrary, ended up surprising me by how much of a proper movie it ended up being. It has one major flaw in Kristen Stewart but the rest of it is pretty damn strong. I was especially impressed by Hemsworth's performance. I'm not someone who thinks that making anything dark and brooding is automatically better but in this case it kinda worked for me.