They are horribly similar softwares. Sometimes I just wish Autodesk would merge them together.
It is only a major nuisance at this moment, they even cost freaking the same at this point and it only makes it more awkward for the designers who are forced to use either one of them at their workplace.
General consensus is that maya is better with animation and 3ds max has tools more suited for modeling of assets for real-time display.
The actual difference is that maya is less user friendly and has cluttered interface while max is generally the preferred option for being more accessible in numerous ways.
But really, the studios use XX or XX probably because that is the software they purchased.