from my experience of the max m14 and the regular m14, my max has upgraded wiring, 6.03 tightbore, nozzle, cylinderhead, pistonhead, torque up gears, either an m130 or m140 and a torque up motor... basically nothing from an off the factory line g&g m14. All the internals are shiny factory upgrades.
It shot somewhere in the neighborhood of 470-480 with .2s out of the box. They are really nicely upgraded guns from what I can tell, even better if the model has harder to get g&g only parts.
The problem is in the last 8 months, prices have dropped dramatically for just about every other brand in canada. Last year when I bought my m14, it was a viable choice given the amount of factory upgrades that I wouldn't have to do myself.
This year, completely different story. There are so many cheaper options at half or even less than half the price of a g&g max that it just makes it not quite worth it to look at anymore. Unless you are buying one of the rarer guns like the EBR, and sigs maybe, and even then, you have to really want the g&g specifically.