I think the HCG/Toynami one is 99,9% accurate..you can see it at the HD-Specials on the new Terminator 4 BluRaydisc..they visit Stan Winston Workshop..there is a great Detailshot of an Original-Endo.Here a comparsion of my HCG/Toynami with the original:

No symetrical and long teeth in the lower jaw like the sideshow..the teeth at the HCG are the right one..same shape and size and not snowwhite.I think the sideshow looks great,but the HCG is the one to have it accurate.I cutted my soundchip at the HCG..now its perfect for me.The sound is the only flaw at this bust..but after cutting one cable its quiet.;-)

No symetrical and long teeth in the lower jaw like the sideshow..the teeth at the HCG are the right one..same shape and size and not snowwhite.I think the sideshow looks great,but the HCG is the one to have it accurate.I cutted my soundchip at the HCG..now its perfect for me.The sound is the only flaw at this bust..but after cutting one cable its quiet.;-)