VHDL vs SystemC library
No, VHDL is like assembly, you get exactly what you ask for and you are designing on a lower level. System C is like a higher level language, and in the end it gets translated to VHDL or Verilog anyways, but you aren't always going to get the lower level optimizations. System C is better if you have a lot of the same things to do, like build image filters with a lot of multiplications and adds. Which would be a real pain to implement in VHDL.