OK, I changed changed the NX05 in the ARC to a SO17 and mineral lens, and added a .33 Ohm resistor to the board.
The result is shown here (picture taken 1m from wall):
ARC with SO17 left, QIII right
Hotspot diameter is about 20-25 cm
Side spill diameter is about 145-150 cm
The modded ARC now easily outperforms the QIII.
Both lights draw about 700 mA from a fresh CR123A,
The ARC gets quite warm, and faster than the QIII.