Simply put, Dexx (as well as femera, and aromasin) prevent aromatization, which is what you want. Nolvaldex - tamoxifen citrate - and Clomid are SERMS and technically anti-estrogens whereas the others are not (but that's a bunch of terminology. They're ALL anti e's). Anyway, Nolvaldex - tamoxifen citrate - and Clomid are actually estrogens which compete for estrogen receptors therefore preventing aromatized estrogen from "docking." MAYBE.
This has been my argument for years. This process is very hit or miss.
And if estrogen isn;t high, Nolvaldex - tamoxifen citrate - and/or clomid will "add" MORE estrogen.
This is why both Nolvaldex - tamoxifen citrate - and clomid can be libido killers.
Nolva is also site specific, making it good to combat gynecomastia, but little else. In my opinion Nolva is an outdated drug with limited use and is often used incorrectly.
Dexx has an advantage over femmera for one very good reason-- it lowers sex hormone binding globulin (as does Proviron and UNLEASHED) so it has a slight libido enhancing effect (as does Proviron and UNLEASHED) whereas Femmera can cause a little libido loss.
I have yet to try aromasin because my combination of dexx and POST CYCLE has been working great but I will be giving it a go soon and I'll report back on the results.