a) The switching regulation is almost lossless. It provides much longer runtime in all modes with any battery just because all battery power is directed to the LEDs, no FET resistance loss.
b) The switching regulation provides stable lumens and its output doesn't depend on the battery charge. As the battery voltage drops down, the regulator increases the amps to keep the wattage and thus the output stable.
c) The new FL33 uses a constant current regulation in all modes, with no PWM, in all range from 0.17lm to 3500lm. Flickerless and silent operation is not the only benefit of this technology. LED runs with much higher efficiency at low amps. The fewer amps are driven into LED, the higher its lumen per watt rating. The constant current fully takes advantage of this feature providing more runtime and increasing battery life.
d) The switching driver operates at a way wider voltage range. You can feed your flashlight with one or two ICR/IMR cells or with two CR123A primaries.