...just kidding, of course.
The things I would consider here are complexity and dimensions...
I personally shy away from unnecessary complexity in a tool, and I would consider the "rotating dimmer switch" unnecessary complexity. It also adds considerable length to the light, which is something that you need to consider if this light is for EDC. The TA series is 30mm longer than the TK series.
One reason I would not consider the TA20 is that it isn't compatible with 18650 Li-Ions. I only use CR123 primaries for storage purposes, so I simply would not use the TA20 if I owned it. The TA21 and the TK11 would be the models I would select from, for this reason.