what is better

[420nitro]

Shaving/milling the heads wil increase compression. It will also throw your intake alighnment off. You will need to check & most likely mill the intake to fit when you mill more then 30-40 thousands off.
As goes for what they will flow depends on who is doing them and on what flow bench. If you are spending that kind of $$ to port the heads then just go buy a set of AFR heads or Twisted Wedge and end all the b/s. Those heads only need work when you are trying to make ALOT of power. Those AFR/Twisted Wedge flow better out of the box, then those other heads fully ported by a expert porter.