I don’t want to derail this conversation, but the whole solution really matters. I have not heard ATC’s nor am I privy to their internals. The correct approach, IMHO is to listen and judge for yourself.
Having said that, I want to point out that just because ATC makes 2 versions of the same speaker box with the same drivers doesn’t mean the choices in the crossover are the same, so a lot of these points about one or the other version being naturally superior are hard to prove. For myself, I would find it nearly impossible to make the same passive and active speaker. The biggest difference between active and passive is that I have to make fewer design compromises in an active speaker.
For instance, I just made an active 3-way center channel with 4th order LR filters between every driver, all drivers in positive polarity. I’d never attempt this as a passive, and would be relegated to 2nd and 3rd order filters and highly unlikely they’d maintain the same polarity. Active, especially with DSP, just makes everything so easy. If I were at ATC, and they asked me to "activate" an existing passive speaker it would be just incredibly tempting to enhance it’s performance when transitioning.
So, point is, no idea of the ATC speakers attempt the same driver crossovers, polarity, etc. so hard to use them as a judge. In fact, it’s just super hard to do a real apples to apples comparison of any active vs. passive speaker. Judge the whole package and do so on a case by case basis.