If you are using a standalone, L-Citrulline is more effective than L-Arginine at raising NO levels in the body...Arginine gets used up by the intestines where Citrulline passes thru and then gets converted into Arginine by the body. However, using both in combination is even better and beats using either by themself.
That being said, I'd get your T levels checked. Depression can be a sign of low T levels and ED is DEFINITELY a sign of low T levels.
Have them run a whole spectrum hormonal profile...
Estradiol, Progesterone, DHEA-S(make sure its DHEA-S and not DHEA), T total and T free, SHBG, and Thyroid.