What are the advantages & disadvantages of NMAKE vs MSDEV /MAKE

I'm trying to automate the building process of a large number of Visual C++ 6.0 projects. I've started by using MSDEV myworkspace.dsw /MAKE ... from command line, but I know I can also gene开发者_运维技巧rate makefiles within the IDE and use NMAKE to build the projects.

Why would using NMAKE be preferrable? It seems like an extra step would be involved in that if I make any changes to one of my project files, I'd have to re-export the makefile before building it from script.