Everyone is entlitled to their opinions (and taste, of course) but Elizabeth as Juliet showed so many emotions during the course of the series, then reduce the judgement of her acting to the neutral/controlled expressions she put on as part of the character's persona is a pretty limited way to look at things, IMO.

And Liz has done what she could, and had to, with Erica's portrayal and the material she got in the scripts. Juliet was a very unique figure and she could add a lot to the creation of the character, and take advantage from the mystery factor here and there. Erica is a more "formulaic", straightforward character, and you have less freedom to fill certain gaps or hint to something with your performance.
Morena stood out among the cast in Season 1, but she also got the most interesting/original material to play with (imo).