XML2 upgrade in moderately driven application

Looking for possible upgrades to one of my commonly used lights. It runs an xml2 at a rated output just over 600lm. From what I can tell most of the newer crew line up would offer minimal gains. Not sure about the 3v xhp options. The sst –40 might offer better runtime with its lower vf but minimal if any gains in output.

Any suggestions or is it pretty neglidgablr without pushing the led harder than it’s driven here?

lower vf only helps runtime if you use a efficient buck converter.resistors in some drivers to set top current limit and 7135 based drivers will burn lots of energy as heat and will be worse with a low vf led.
some of the high bin xp-l may give you more at the same drive level but its not likely to be all that visible in real use.
takes a doubling of brightness to be easily perceived.