It's too late into the night to find the threads and link them, but somewhere here on ECF there have been discussions concerning battery brands and battery types, performance and longivity. From what I remember, and anyone can correct me if I am wrong, is that AW makes the best
batteries by far. The Trustfire and Ultrafire
batteries can be considered to be cheaper, lesser brands, less dependable with over-inflated specs.
Of the two
batteries you list to compare: the AW IMR is a high drain type, meaning it can provide more bursts of power that could be useful for low resistance attys or cartos. Not protected, but is safer chemistry not needing protection circuitry. Although its 2000 mAh rating is lower than the protected Ultrafire 2600 mAh, its lifetime battery life can be expected to outlive the Ultrafire over time. That's what I think I learned in a nutshell. Synopis: You'll likely be happier with the AW over the long term.