Jen is my fave along with Elena. And I like Lindsay too.
In terms of technique, consistency, power and aggression, Elena's is much better in all those departments in comparison to Serena, Lindsay and Jen. Serena's technique is shaky, Jen isn't aggressive enough with her FH and Lindsays can break down pretty often too.
Elena's FH is the money shot. The winners, the returns and the groundies she can hit on that wing are amazing. Especially towards the end of the second set today.