What are the differences between a thermoformed vinyl coating and melamine?
Melamine doors are square cut. An have edge strip glued on (you see a line where it's glued) 

Vinyl doors are wrapped in vinyl
Allowing them to have patterns on the door. An round edges. 

Melamine doors dont quite look as good in my option. 
But they are cheaper an still look good. With the right colour an handles they will look good. 

You also have tho option of 2-pac painted doors (my option there the best)
Better finish. 
They cost more. 
But can scratch easier