Questions and assertions at the same time.
For a given brightness design goal, many smaller LEDs may give lower junction temperatures/long life for each because the junction to case thermal resistance may be smaller and the heat is spread over a larger sink.
Also, many LEDs gives redundancy which gives the light a graceful failure mode rather than all or nothing.
Battery life should be better with one LED because of higher luminous efficacy at higher drive currents?
If LEDs are wired in parallel your penultimate assertion can be true. Keep in mind that parallel LEDs introduce the possibility for other modes of failure, however rare.
Your last assertion is not true. Driving multiple emitters allows you to achieve a given amount of flux with less power than driving one of the same emitter. For real world use in flashlights this balances out by the reduced lux produced by multi-LED setups given a fixed flashlight size compared with fewer or a single harder-driven emitter.
If you want throw - the smallest emitter at the highest current that doesn’t make it smoke is best.
For sheer output, the more emitters the merrier.
Lotsa flood - but quantity has a quality all of its own.
folks. . .I’ll have to think on this.
To get the best throw you need the smallest point source with the greatest surface brightness but multiple emitters in parallel will give a higher lumen count(same emitter as single) because they are more efficient at lower drive currents.