Nothing, GH is GH. Assuming that te Serostim is hologram and is legit. Saizen is sold in lower dosed vials, more for children. Both are good, Serostim being the better buy because of price.
Big BX - thanks bro. I thought that was true but wanted to make sure since one is coming from script and the other is a source buy and you are right the Saizen is only 15iu and not as good a buy.