VixSkin cocks are very high quality, and they do look kinda realistic, but they're not the MOST realistic. The uniform color throws things off, since flesh cocks have tone variation across the skin. Also vanilla VixSkin is just ridiculously pale.
I think the Tommy Gunn is the most realistic looking. But the most realistic looking isn't always the highest quality or the best to use. It's what I would go with if I was only interested in realism, not quality.