Defo better but not the best but you should achieve around 90% or more efficiency with normal load from ESP, maybe 0.5 day more. If you look at efficiency curve you will notice that it is terrible for low current which is the problem here.
BTW you should use Buck/Boost converter as operating voltage of 18650 is from 3v-4.2v
It's also quite important to note that efficiency during deep sleep will most likely drop to as low as 50% or even less...
Actually put an output from your DC/DC converter to 3V this will most likely give you bit more juice out of battery.
