[BrianG]

As both controllers are relatively new, it's hard to say which one is more reliable. Generally speaking, the more robustly built one will last longer since the components aren't strained. It also depends on the design quality of the rest of the circuit; for instance: if the circuit traces aren't large enough to pass the required current, the resulting heat can, over time, damage nearby components.

IIRC, I think there has been one or two Quarks that have burned up so far, and maybe one MM, but I'm not sure. It's hard to say if those were simply lemons, or legitimate faults from being pushed too hard.