Use whichever you can afford and feel comfortable with.
Armidex and Femara do aggravated ones lipid profiles but if you keep the use of these compounds to a reasonable length of time and keep a fairly clean diet, you will be o.k.
Aromasin affects the lipid profiles much less than A and F but costs quite a bit and its not readily available as A and F are now.
My advice, experiment with all of them and come to your own conclusion to what works and feels better for you.