Wild guess... get other input -- but my guess is rHGH implies that it was made via rDNA (recombining the genes of some bug like Escherichia coli so it's programmed to make the GH). If that's the case, then the non-R version would be that harvested from human cadavers (pituitary glands, I think).
I don't know the pharmacological differences between the two but I know a few people on non-synthetic HGH died of Creutzfeld-Jakob disease which is a bug you get when you mess around with things derrived from the brains of corpses. CJD is basically BSE (mad cow) for humans -- it's horrible stuff and 100% fatal. Obviosly synthetic HGH users wouldn't have that risk since their HGH came from a bacteria, not a dead person's brain.
All synthetic for me

I don't even know if they make the non-synthetic stuff anymore.
Thanks,