I've had my hands on both, but only own the 2L, so I think I can give a basic review. In terms of the LED, both are on an equal playing field in terms of brightness and beam quality (The 2L only comes in white LEDs of course, and was compared against a White A2). In xenon mode, the A2 is brighter (I would say maybe about 10 lumens?), with a more focused, but oblong beam. Thus, the A2 will throw farther. The 2L has a wider beam, even when focused to its tightest, similar to the L4. The beam quality is relatively smooth.
Here's my take on the two lights. Both of are of extremely high quality in their respective fields. The A2 is smaller, and better suited for EDC. Its got the HAIII, if you really need that. And its got the SF name, quality, and the pre-focused beam, which some people like. And the TT-2L has the awkward switching mechanism which may inept if your job depends on a two stage tailcap. But the bottom line, I don't think the A2 is worth the extra $100+. The 2L is a perfectly fine light, and I don't see any immediate tangible advantages the A2 has over the 2L that is worth laying down your wallet for. Just my 2 cents.