I wouldn't mind cr123a as long as there's a noticeable difference.
Check out the FourSevens Quark Pro line to compare:
1xCR123A (QPL): 205 lumens for one hour max output
1xAA (QPA): 109 lumens for one hour max output
2xCR123A (QP2L): 230 lumens for two hours max output
2xAA (QP2A): 205 lumens for one hour max output
That's a pretty significant difference!
(I have no affiliation with any flashlight manufacturer or vendor other than as a customer)