Everybody's making good points and I hardly need to add anything.

Nevertheless...

The first three all look terrible to me. Why the purple lighting?

Of the second three, the commercial one looks far better, IMO, but I can do better.

All this talk of "nodes do make a big impact" and "can't help render times" seems based on no actual stated measurements. Did you consider that you should actually time these renders and make an argument about how much one more node costs?

On a typical high-quality render my measurements show that most nodes are very fast indeed. 

Let's do an extreme test. Given 1000 by 1000 (a one-million-pixel) image with Min Shading Rate at 1 every node will be evaluated exactly 1 million times. Placing a one-sided square to fill the render and changing the shader I can measure the cost of any set of nodes. 

Of course this is overkill, since you rarely fill the image with any single shader, but let's measure for the sake of argument.

Some representative examples: (times are on my machine which is Pentium 4 3Ghz, using P6)

Basic Render (Diffuse_Value = 0, Specular_Value = 0 - no nodes): 19 seconds
Diffuse Node: +1 second
Glossy Node: +1 second
Diffuse+Specular (using Color_Math to add them): +2 seconds
100 Add nodes: +17 seconds
Diffuse+Specular+100 Color_Math:Add Nodes: +22 seconds
10 Fractal_Sum added together with 9 Color_Math:Add: +12 seconds
My most complex skin shader (freckles, moles, splotches, bump, sss, 24 nodes): +18 seconds
My Ultra Basic Skin Shader - UBSS (freckles, moles, splotches, bump, sss, 15 nodes): +15 seconds
Glenn Plaid  with 6 layers of fibers (283 nodes): +88 seconds

So some nodes are really cheap (math nodes) at approximately .17 to .2 seconds per megapixel. This is including two multiplies on each one as I didn't use "1" as the coefficients, but .6 and .4.

Basic lighting nodes are about 1 second per megapixel. This is impressive considering they must do cosines and powers.

Noise-based nodes are also about 1 second per megapixel. Also impressive, since an 8-octave Fractal Sum is a lot of math.

A good skin shader costs 15 seconds per megapixel.

A great skin shader costs 18 seconds per megapixel.

I don't really get what the issue is. 

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)