I like both names, but I very slightly prefer
Sabrina because the 'b' makes it sound less slippery smooth.
Name Associations:
Sabrina-
Sabrina, the teenage witch, and the character played by
Audrey Hepburn in the old movie "
Sabrina" are my first thoughts. There may also be a myth about a
Sabrina who inhabits a river that reflects her moods. She rides in a chariot pulled by dolphins and may be a sea nymph.
Serena- I associate
Serena with the mythological Sirens for some reason, so a mermaid comes to mind. There is also a
Georgette Heyer novel with a character named
Serena, who is strong willed, redheaded beauty. And there is the athlete
Serena Williams.