This topic of comparison between Poser shader tree versus SkinVue versus normal Vue material has come up in this forum several times. There's a thread where there are some visual comparisons, which could help to the decision, here:
http://www.renderosity.com/mod/forumpro/showthread.php?message_id=3172332&ebot_calc_page#message_3172332

I have Vista64 with 8GB of RAM so memory is not a problem but even so I do not use Poser shader tree. I really do not like how skin looks in the render. I always inject SkinVue in a 32 bit machine and then transport the object to Vista64.

As bruno021 said, SkinVue colapses some of the texture parts, which is perfect for adjusting the material properties. Instead of having to adjust those in 20 different texture parts, you only have to do it in one place.

So far, there are only two things with which I had some problems in SkinVue:
a) Eyes: in SkinVue I was never able to make them look right in extreme close-ups, like if you fill the screen with only the face (normal close-ups, half body, work fairly well). I still prefer native Vue for these extreme close-ups.
b) Extreme light conditions, with lots of ambient light and radiosity, like the environments of InteriorPak: the skin from SkinVue appears with some ugly spots (not radiosity spots, something else).