Sanyo batteries work, but they are far from ideal. If you could get them for cheap, maybe I would use them for a class or something else like practice with your light. But to be honest, the cost difference is so small I doubt I would use anything other than the SF batteries.
Compared to the Sanyo's the SF batteires put out a whiter light, for longer. I have not done extensive testing but I have been using Surefires since long before they had their own batteries. Back then all I would use is Duracells and Energizers. Both are good batteries (with Duracell getting the edge). Aside from those two brands, I have not found another brand 123a worth a crap.
Between the SF, Duracell and Energizer, I found the SF's to make the biggest difference in 3 battery or bigger lights. With these larger, more power hungry and demanding lights, the SF batteries gave a whiter light and longer life. In the 2 battery and smaller lights, I didnt notice much of a difference between the 3 brands.
With SF battery prices being so low, I havent found a reason to get a different battery.