Passive vs Active
What are the advantages of the passive version of the M1 pickup?
You have to run it through a DI. And you can run the active version of the pickup through the DI anyway... So what advantages does it have? Well besides some people not wanting to worry about batteries.
It's mostly about people not wanting to mess with batteries. Also, the passive M1 is supplied with a 10' cable for exiting the soundhole for those players who don't wish to have the 1/2" hold drilled in the tail block to have the 1/4" output jack permanently installed.
The passive M1 can also be connected as an auxiliary signal to another system, such as any of LR Baggs' endpin preamp systems or in place of either stock source(Element or iBeam) in an iMIX system. Not so straight-forward with the M1Active due to the power and switching circuits.