According to studies I've read, it is supposed to be the most suitable for clinical depression
while on treatment.
I don't know about off treatment.
Here is a link for the comparison of the two:
Escitalopram versus citalopram: the surprising role of the R-enantiomer.
Sánchez C, Bøgesø KP, Ebert B, Reines EH, Braestrup C.
Research and Development, H. Lundbeck A/S, Ottiliavej 9, 2500 Valby Copenhagen, Denmark.