There are a couple of things that I would like to add to Hop's excellent post. First, the PB16 doesn't really have a tuning point of 13Hz. That was an early marketing statement that didn't hold up. A sub should be strongest right at its port tune, or a little below, and the PB16 measures about the same as a PB13 Ultra at 12.5Hz. I believe that the actual port tune is about 16Hz. Since most people are trying to get into about the mid-teens in-room, a 16Hz port tune (or even 17Hz) isn't bad at all.
Second, what the PB16 does have is max output that is equivalent to a JTR Captivator 1400 from 35Hz down to 16Hz, or a little lower. Probably by about 15Hz, the Cap 1400 starts to pull ahead, but that also isn't bad at all for a 15.5" driver, compared to an 18" driver, from a sub maker whose DSP is intended for maximum low-frequency extension. JTR is the king when it comes to low-frequency output from ported (and most sealed) subs. The PB16 used all of its slightly larger cabinet volume, its bigger stronger driver, and its slightly more powerful amplifier in the low-bass (<35Hz) range where SVS believed that people would appreciate it most. And, they got ~4db more output than the PB13 in that range.
I can attest to the fact that the PB16 has a heavier, weightier sound/feel to it than the PB13, due to that concentration of max SPL in the very low-frequencies, as I have had both models at the same time. There have been a few reports of the PB16 chuffing more easily than the PB13 does, and I believe that is correct. But, I agree with Hop that any ported sub will chuff under the right circumstances, and the number of chuffing PB16's, considering the hundreds sold, has been very small. I have three PB16's, for instance, and none of mine has ever chuffed. But then, they are properly deployed and calibrated.
In order to more completely eliminate the potential chuffing problem, compared to the PB13, the PB16 would have needed an even larger cabinet to accommodate 4" ports. It currently has the same 3.5" ports that the PB13 has, with a more powerful amplifier, and more SPL deliberately concentrated into the very low-bass region. Subs typically chuff near their tuning points, so with more amplifier power concentrated there it can chuff a little more easily than the PB13. But, even then, if the subs are functioning properly, the chuffing seems limited to very demanding material, and is typically only an occasional problem with a few subs.
I try to never encourage other people to buy what I have unless they are specifically looking for encouragement. I believe that, depending on a person's specific goals, there are subs that will produce even more max output at comparable or better prices. And, the alternative choices can be very good indeed. But, for people who like the aesthetics, or the features, or the total SVS package (including brand loyalty, for what that may be worth) the PB16 is still a very fine subwoofer.
Edit: I should probably add that there is a lot more to a good subwoofer than the size of the driver, or it's max output at a particular frequency. All of the professional and owner reviews of the PB16 I have seen have been very favorable with respect to its low-distortion and overall sound quality.