As several have said, both are great devices, neither will make you sad. I researched heavily, and chose Darwin. "Regulated" is the key word here. I believe that Darwin is the only regulated device, available at any price. "Man, you're only aping at 5.684 volts? I am vaping at 5.935 volts, IT IS SO MUCH BETTER". Many just want More Voltage. That is only one number in the equation.
All of the devices are basically power sources with atty/cartos attached. The atty/carto is what give us the actual vaping experience. The job of the battery is to just provide power to the atty/carto. As that changes, so does the experience.
Any one number is meaningless, it's all that delicate ballet of Ohm's Law. Ohm's law is not absolute, resistance changes with heat, and all these things are little heaters!
The convenience of changing things is just that, a convenience. Some like to swap parts out, and consult a chart to give consistency, some do not. The preference of a tube, box or slab is also just that, a preference.
Performance-wise, if it's regulated, it will compensate for atty aging, crud buildup, battery degradation. Using HR atty/cartos are preferred with Darwin because it will draw less amps, and that is what gives better battery life, with the same vaping experience.
Try them both out if possible, and see what works for you!