Hven't tried the Poison Golem, but I'm not entirely sure they're comparable. The Golem has a poison aura, no? And is a singular entity, with steeper path requirements. Manifest Vitriol is only 2W+1F, and only requires 2 gems to cast.
I'd venture to say that really in most cases you can cast one or the other, you don't tend to get much choice between the two.
