...I am not as knowledgeable on the 5761 bulb as some but have done 3 so far using C LiIons and NiMH AA with several different reflectors. I find the beam less useful and less pleasing than the 1185 (the bulb has a wide transverse and therefore difficult to focus filament). But maybe I'm missing something because some folks sure like these things (comments from 5761 experts welcome here). This setup does not like AWs C LiIons (very borderline on triggering protection circuits and there is voltage sag, too) so is best run on NiMH IMO but the lower voltage needs mean you won't pack the tube with a full set of AA NiMHs (9 in a stock tube for an 1185 or 12 in a quadbore for 50W or 100W bulbs) if you use a 3D. That equals lost run time, of course....
I have to agree the 1185 on appropriate power sources has a very fine and white beam. If you do not put the 5761 side by side you cannot be really subjective because the outputs and the differences between them is suttle.
The 5761 has a larger hot spot with the smooth reflectors I use, I suspect if you use LOP or courser this difference will not be as apparent. The 1185 is white the 5761 more yellow in appearance. Yellow is sometimes prefered to increase contrast outdoors for greens and humid air.
The 1185 uses higher voltage so if the size of the light is critical then a 5761 works better. 2C-size 5761 are easy to build, I guess the smallest for the 1185 would be a 3C-size. In larger light bodies the run time can be compensated for by building higher AH packs for the 5761. E.g. the MagCharger can hold a 5400mAh pack of Powerex AA and run the 5761 for almost and hour and the 1185 with the same brand of batteries you get a 2700 mAh pack, 58 minutes V. 49.
The two lights are very close in function. I personally like throw and bright lights, I measure the utility like this for me:
5761
lower voltage allows smaller lights or larger Ah packs
larger hot spot in the beam
light spectrum condusive to my environment.
Slightly more light output, more noticable when lighting up a local area infront of you
Slightly brighter, a little more throw
1185
very bright white light, optical illusion is it is brighter because things look clearer
beam pattern clean without many arifacts
lower light temperatures
lower Amperage
medium size light bodies work best.
cannot get a very small light body of the mod
edit here.
5761 will trigger AW protection circuits if the light is built well without too much residual inherent resistance. AW dirvers or the $0.70 NTC soft start fix that problem, both allow either the 1185 or 5761 a higher run voltage than a direct drive. AW cells are at their limit with 5761 and I believe some 1185 set ups will top that style of 5761 mod. I recently built a 1185 on 3 AW cells and it really gave my AW powered 5761 a whupping! It,1185, just was too long for my most often used appliacation. More lumens can be coaxed from from the 5761 with A123, emoli or NiMh packs made with high drain batteries.
As in all mods, the key is the Vbulb, voltage to the bulb for getting the most lumens out of it.