You'll have to define "best," and what you consider "3D drawing" while you're at it... As Greg mentioned, prices and capabilities of different software packages vary wildly.
for 3d modeling of pipe I would recommend Inventor that last time i used it, it had the ability to do piping pretty easily. I am a personal fan of solidworks, it can do piping pretty easily with a simple sweep. like stated above it is all about your budget
Google sketch-up is free and has a "follow" utility that you could use to run pipe. If you can afford something better, I would go with most anything else though. Piping is easy in solid works and Catia but both cost several thousand dollars unless you are a student in which case they cost a hundred or so dollars for a year long license.