As far as going between nolva and letro, i would try nolva first and see how it works out for you, especially if your gyno is only mild and isnt worsening at a fast rate. Letro wipes out your endocrine system, and for me as far as libido ive been in bed with 4 girls since i started and haven't been able to go past 3rd.... literally completely obliterated all my libido. On the brighter side, my gyno went from pretty bad, to unnoticable, to virtually completely gone (ill be using it for another week or so until its non-existent or stops getting smaller). But definately try nolva first, especially because letro takes a TON of estrogen out of your body. Some sides i experienced on letro:
No Libido
Not being able to get it up
Headaches
Joint pain (moderate, some people have it much worse)
Extreme lethargy at times
So best of luck, try nolva first. and make sure wherever you get it from, its legit.
-Trav