Answer to Question 1
Rapid prototyping allows a part to be made directly from a CAD rendering. This ensured that the prototype is the same as the drawing. Also, the time to create the prototype is much shorter. In some rapid prototyping methods, the material of the prototype can even be the same as the material of the part, thus allowing mechanical prove-out as well as dimensional verification.
Answer to Question 2
Regrind material is rejected product that has been chopped into small particles so that it can be reprocessed to make new parts. This is an advantage of thermoplastics. With PVC, however, the tendency to degrade is so pronounced that each time the PVC is heated, the degrading gets worse. To further complicate the matter, the degradation of PVC is autocatalytic, meaning that the decomposition happens faster as more is formed
Exponential versus logistic growth.
A Taxonomic classification of hominins versus hominids.
Bat versus Dorian from The Mask
Aldose versus ketose
Explanation of endocrine versus exocrine.
Government Corruption versus GDP per Capita, 2009