You are prob comparing lux numbers. A 300 lumen p60 will have a brighter hotspot than a 800 lumen. The smaller leds focus better in a small reflector, so the hotspot will be brighter (more lux), but will have less overall output (lumens).
Hi Jorn I've been slightly more scientific than that. I've aimed both lights at the same position of the ceiling and alternated switching them on and off, while staring at the walls. I agree it is difficult to judge when you have different hot spots and beam patterns. However I can say the drop-in is less bright in the ceiling reflection test than my 320 lumen Olight, and about the same as a P7 Led Lenser (170 lumen). The beam range is slightly better for the drop-in versus the Olight, because it has a more focussed hot spot, but no better than the LL (which you can focus).
I am wondering if it is something to do with the driver in the Ultrafire 501B body. Maybe it can't supply enough current?