You can REALLY see the influence of Sailor Moon and of Sailor Stars. Especially in the plot of having a rivalry of "other world" Senshi/Cure and Earth Senshi/Cures as well as the fact we having someone singing to summon a princess, and that princess is young/a baby (with heart odongo hairstyles too!). Also the enemies are a human looking group (Sailor Moon kept this for all seasons) who bicker amongst themselves in their own bar (SuperS reference?). The enemies are all people with corrupt hearts (star seeds/dream mirrors/etc.) which are then purified back to being human.
-Cure Diamond′s pose is similar to Sailor Venus′ pose.
-Regina looks like Minako Aino/Sailor Venus.
-Ai is similar to Chibi Chibi.
-Cure Sword and Sailors Starlights came from another dimension and became idols to search for a princess.
Both anime have male characters that transform into magical girls. Twintails is more of a sci-fi magical girl show while Sailor Stars is more of a "magic" mahou shoujo. They both have a "monster of the week" feel.
The same maho-shoujo style and quite similar plot:
- the heroine's beloved is somewhere far (namely in the USA) and they will meet each other someday;
- meanwhile another candidate for being beloved appeared (by the way both guys are singers ;))
The difference is in heroine's choice and plot variations. Watch both: the feeling is pretty the same.
Personally, I love them both. I love the 90's era style of anime that they both portray fantastically. Tons of romance and emotional monologues in both :) Chibiusa in Sailor Moon is Maika's Voice Actor. Nuriko's VA is Yaten's too (little bit of gender bender in both there) :) Love one, you'll enjoy them both