Not really much of a difference, really. The files are the same. The mpt's
will be saved by default to the template directory while mpp's are saved to
the data directory. Opening and mpp, editing it, and hitting "save" doesn't
prompt for a new file name. Opening an mpt and editing prompts for a new
filename when saved and changes the extension of the edited file to mpp by
default. That's really about it.
Here's how I'd use each. Imagine you're a real estate developer building a
housing subdivision offering houses with 5 different floor plans. Each
model of house has a basic construction plan but each one you build is
somewhat customized for the client. I'd create my generic plans for each
model and save them as an mpt template. When Mr & Mrs Smith purchase one of
your 3 bedroom bungalows, you create a new project file based on the
3btbunglow.mpt template, changing the Project Start date in the new file as
approriate and customizing the plan as necessary to incorporate the client's
preferences and options, then save it as Smith'sBungalow.mpp, upon which it
becomes the working plan for their specific unit.
