- Were you intending to take only one of these single-cell lights? - pending input from whomever?
- Which battery types you were considering for deployment?
- What about expected usage? Heavy duty usage or light personal usage?
If primary cells, then the CR123-based light is usually brighter due to the higher cell voltage. Depending on where you are deploying to, AA primary cells are likely more readily available whereas CR123 cells may not be. Note that some locations/deployments have solar recharging panels.
If rechargeables, then which kind for which light?
If AA rechargeables, then by all means ensure that you take the LSD (low-self-discharge) types and a "smart" charger.
If RCR123 cells, there is another choice to make - protected or unprotected? Protected means that the circuit in the cell will _cut off_ the light if the cell voltage drops too far. Meaning you will suddenly lose your illumination - no warning. Unprotected means that the light can run the cell down below the recommended cut-off for Li-xxx cells.
The chemistry of the Li-xxx cells will also make a difference. The LiFePO4 or the LiMN cells are considered "safer" and more tolerant of abuse as opposed to Li-Ion (LiCo) cells.
Basically RCR123 cells of various chemistries are more "fiddly" than the AA NiMh LSD cells.
My recommendation? Insufficient input info for a decision..
ex-mil, '64-'72.