For me, Fem shuts down my sex drive too much, I only use it when I really need it, I stick to arimidex (liquidex) and maybe at times mix in fem. From experience and from working with others, I'd say it's at least 5-10x more effective (very strong)...but I woldn't say 30x stronger.
I found 50mg proviron/40mg nolvadex to be more effective than femara. I will probably decrease the proviron to 25mg/day at the end of this month. I am super prone to estrogen gyno.