I haven't used the ATI, but my understanding is that the active cooling will get you more output and longer bulb life than the Tek. IME, the problem with the passive cooled Tek is that if you use the splash guard you'll have heat problems, but the reflector will corrode (quickly) if you don't.
I'm going to mod fans into my Tek. The new Tek elite has active cooling, but is $100+ more.