Save all pics and put them in a single folder so that you can better compare them.

 

Conclusion:

1. For outside renders, IDL only makes shadows darker. Any "color bleed" isn't noticeable.

(Unless you do "neon lights at night" type renders.)

2. For background figures, lack of SSS is hardly noticeable.

(You can notice a slight difference at the eyes)

3. You can get a very decent render out of older Poser versions without GC using just old fashioned infinite lights. 

(Speed is exactly the same, too)

 

Is it a good thing to have SSS and IDL and GC ?

Yes, NOW that PP 2012 can handle all this stuff properly, my default scene has GC and SSS enabled.

But there is still and never was a reason to get all uppity and declare any other lightning techniques obsolete.

If you don't now what you're doing, neither GC nor SSS nor IDL won't help you.