On the sealed vs ported debate...
If you look at basic subwoofers of either style, the ported is usually tuned to provide a flat FR to the lowest frequency possible. While the sealed will often start to roll off in the 40's or even 50Hz range.
Given that info, you would expect the ported to sound better. However, the problem is that you have room gain and these FR measurements were taken using an anechoic chamber (or using a method that approximates an anechoic chamber).
Without knowing better, we tend to tuck the subwoofer against a wall or even in a corner. When we do this, we are adding lots of room gain at those lowest frequences. Here is a graph courtesy of SVS which shows the measured (anechoic) frequency response of the sub (in purple) and the response after typical room gain (blue). Looking at this, I would guess they did a little EQ via a DSP to push the rolloff down to around 34Hz (instead of in the 40's). However, the important concept here is that if the anechoic measurement was flat, then the in room response (after room gain) would be about 1dB too hot at 30Hz and 5 dB too hot at 20Hz.
For music, 5dB too hot at 20Hz will not be a good experience (and I have seen as much at 10dB room gain if you were to put the sub in a corner) for music! Any content that low will sound bloated and muddy up the rest of your sound!
However, a well designed ported sub like the XTZ has options to plug the ports (one or both) and also a toggle to switch between a couple or three EQ curves. This allows you to replicate the curve of a sealed subwoofer, allowing you to avoid the bloated bass of the anechoic flat sub after room gain is added.
Like I (and SVS) said the above reflects a "typical" amount of room gain. They use the term "typical" loosely, because, in actuality, the amount of room gain can vary wildly! So the various combinations of plugs and EQ settings give you a decent array of tuning options to better accommodate whatever room gain you have! That is why I can only recommend a ported sub that has the port plugs and EQ settings to allow you to tune it to your room.*
*somebody is going to call me out on this, because for a budget sub, I often recommend the Dayton Audio SUB-1200. However the SUB-1200 is not tuned to get the deepest flattest (anechoic) FR possible. The port on the SUB-1200 seems to simply lower the rolloff point providing a FR more like the SVS SB2000 curve above, so it is not a typical ported sub.
There is much more that can be said on this topic, but hopefully this bit of explanation makes sense and gives you a better understanding of why, despite your previous experience with ported, a modern well designed ported sub will deliver very good performance!
