If you match drivers and other factors and made one sub vented and the other sealed, the sealed sub will start to drop off higher and have a less impressive low end. The sealed box will almost be twice as large and thus more efficient. Room gain starts around 40 Hz. The longer the room, the less the gain according to this formula: C is the speed of sound and L is the length of the room
C/2*L
1130/2* 20=28.5 Hz so you will start gain 12 db/octave starting at 28.5.. This mean at 14Hz you will be up 12 db. Room gain is not boundary gain which is usually 2-5 db. If the length is 30 ft : 1130/2*30= 18 Hz. So you will be up 12 db at 9 Hz. So the gain is less and, this room gain has a greater effect on sealed subs. In large rooms it is better to get a sub that is vented and not chase after the low end since it will be harder to acheive. Getting drivers with more excursion can lead to more distortion. A sealed sub may have a higher low end than a vented sub below it tunning since the vented sub output will drop off like a rock in free fall, lol. Even more wattage will not solve everything. I can't get peak performance out of my Chase subs because even the most demanding movies only come close to using the 800 watt/ RMS and nowhere near the 1600 watt peak usage. With OHF/ Oblivion require no more than 600-700 watts during the most intense scenes at reference level. To get the peak performance I would have to do some type of sweep to see the watts peak near 1600, which is not needed for HT.
The main reason I have sealed subs is due to their size compared to having vented subs with 18 in. drivers. I like subs with a good mid bass thump ( 40-80 Hz) since I have a large room and the compromise is on the low end. Some of the new movies have stuff in the 3-10 Hz region and sealed sub can reproduce this with the right driver and power supply. A ported sub can be damaged trying to get more output below it's tunning which is usually around 20-25 Hz for good ported sub. Some vented subs may go down to 15 Hz..
The Triax benefits from 3 drivers, sealed, and a powerful amp. It is definetly a LFE moster.