which one: subculture M or B

if you could only get one which one would you get sub culture M or B? plus any tips on using either of these? this is for a aero/hydro setup.

Even though its 4 months later, for future reference-> the answer would be Subculture-M (for me at least). This one builds up a fungus called mycorrhizae which allows the roots to absorb nutrients and water more efficiently. The strands of fungus act similar to roots and they act as an extension to them resulting in a larger yield.

Subculture- B helps protect plants against temp. extremes, nutrient imbalances and drought.

hope my writing makes sense- took forever to write