Is not the dimension, CR123/18650/14500, that tell you the characteristics but the technology used to build the cell, also if you are right with cr123 are called the disposable litio, rechargeable are rcr123/cr123r/16340 xD
btw i think that AA/14500 flashlight format is better, most of disposable litio are able of run at critical temperature, like cheap energizer ultimate(litio 1,5v) that run at -40C, if you want top performance can buy a disposable li-socl 14500 high capacity and able to run up -55C ... but take care it explode if short cutted like commons unprotected li-ion, sry maybe is just my problem I dislike cr123 batteries coz I wasted a fortune like 10 years ago to make run my photocamera(was 7$ each cr123 xD)
for a budget portable 18650 xml maybe that 504b or uf-2100(have a too floody spot but is very compact and bright, became hot quickly in high)
P.S. welcome :)