Which is better for a DBA (Swarm); powered subs or unpowered?

A phase control does not adjust the timing. If you are 10 feet from 1 sub and 5 from another there is a time delta between the arrival of the two wavefronts.

Some people like this fat bass. 

All-Pass phase controls operate at only a single frequency with varying degrees of shift across the passband.
For example, the control 0° position 90° frequency could be 2.5KHz and the 180° position 90° frequency could be < 5Hz.
See  http://www.ielogical.com/assets/SubTerrBlues/PhaseControl.png for how an All-Pass phase control affects frequency.  http://www.ielogical.com/assets/SubTerrBlues covers integrating bass properly.

Note that the phase is not constant across the sub's range. To have constant phase, you must have a delay line or physically move the sub.

Thanks for all the new responses! Let's see if I have this right:

@ieales doesn't like Dayton subs b/c they have "no delay so there is time smearing. What you end up with is a fat, detail-less low end pillow."

@b_limo seems to agree with @ieales, at least to the extent that "with the dayton amp, you aren’t able to adjust [the phase of] each one independent from the other", which is needed if the subs aren't equally spaced from the listening position. Makes sense.

@clearthink also seems to agree with @ieales, unless the listener likes loud, thumping bass (I do not, unless I'm wasted and listening to loud, poorly produced classic rock (which does happen, but not as often as I'd like).

@audiorusty seems to lean toward powered subs over one bass amp, because they have more individual control. But he cautions that DBAs are more easy to integrate, since you only have one amp to adjust. My response would be that I don't enjoy spending time tweaking my speaker settings, but if that's what I need to do to get what I consider to be "good sound", I will put up with it. Score one for powered subs. (since you asked, my taste is generally 60's-70's folk, prog rock and classic rock at moderate volume (85-90 dB) for enjoyment, and classical at lower volume for background while working or going to sleep (but I still want it to sound clean). Not so much jazz.

@heaudio has a LOT of good info regarding the difference between getting the time delays right vs getting the phase right, and I have sooooo many questions. He seems to think you can get this right with a well implemented DBA, but I'm not sure how. If he has time to discuss it more, I'd love to know how to text him (or email, phone, whatever).

@millercarbon initially gave some very useful input, and seems to recommend Dayton(s) in a DBA, but my last round of questions scared him away and he has moved on. Nevertheless, I thank him again for all his advice.

So, after all these responses, I have a lot better understanding of the issues, but am no closer to deciding whether I should buy a Dayton and cheap passives, or buy two better quality actives and save my pennies for 2 more.  Maybe the answer is "it doesn't matter", but I really hate that answer... Thanks for hearing me out.  Peace, and enjoy the music!

Distributed bass arrays do not result in "fat" bass.

By FAT I mean that unless time correction is implemented the separate sub signals will arrive spread over several milliseconds.

The beater whack on a bass drum will arrive asynchronously to the head resonance, which will arrive multiple times. Depending on the room, subs and positioning, some may arrive before the beater and some after.

IMO, it's as unlistenable as MP3 which are only acceptable in mono.

Perhaps it's because I sat so long in a recording engineer's chair, but there is ONE spot that has the correct image. Period. I never worked in any studio where the monitors, if they were time aligned, were not aligned at the engineers seat. NO STUDIO EVER had distributed bass.