So does the stampede 4x4's durability measure up to the slash 4x4? I ve read some threads here about the stampede and there seems to be more broken axles than you would find in a slash 4x4.

Seems mostly because it has heavier tires and rims. From my experience, heavier tires and rims usually mean more wear on the driveline and more prone to breakage in the axles and bending?

I got a new Stampede 4x4 and haven't even played with it yet! (busy with work)