Hey guys. Been gone a while: Got a new job that's keeping me too busy to lurk on the forum

Ported and passive radiator subs are both built on the same concept. Look up Helmholz Resonator. It's the same concept as blowing on the neck of a bottle: The smaller the volume the higher the pitch.

The ported sub relies on the mass and springiness of the air in the port while the passive radiator relies on the mass and springiness of the passive radiator. The passive radiators are cool becasue you can control the mass and springiness directly instead of indirectly by changing the volume of the port.

So you should be able to get similar performance out of either system but you have to make different tradeoffs. I would image that any differences you're hearing are due to the individual designs and not whether one technology is better than the other.

Having said that: One advantage of passive radiators is that you don't have to worry about port noise.