If you are running in a class, the rules will most likely not allow modifying the pipe or muffler. If not required to run a specific muffler, the modified muffler is the best as far as restriction (other than no muffler).
This is a new one, is pipe porting something a shop or builder is pushing on you? Hold your gasket against the port make sure that the opening in the gasket is not overhanging the exhaust port, now hold the gasket against the flange on the pipe, use a magic marker and mark the points that that are smaller than the opening. Use a dremel or small file and taper the opening to be larger than the gasket opening. Check your rules
A ported weenie pipe helps direct the gases into the pipe. Even thou the muffler is the major restrictor in this equation rounding or shaping the entrance of the pipe reduces turbulence at the exit of the exhaust port, and most weenie pipes made have some type of rounding or port matching. A big pipe is much bigger and has multiple stages there for flows better and should not need special porting. Not saying it wouldn't help. And as stated above port matching the gasket helps flow and reduces the gasket blowing out on any header.