The response characteristics are different between the two. A sealed sub should produce lower bass compared to most typical ported enclosures because they are often tuned a bit high, say 35hz or so so that they sound louder because their sensitivity is higher and they can use a smaller amplifier to drive them (its a cost saving measure), but their lowest bass is compromised. A sub with say a 35hz tuning really should have a low pass filter that blocks bass much below the tuning frequency if one expects bass much lower than the tuning frequency from whatever source they are using, because the woofer starts to unload as you get lower below the tuning frequency, and it's easier to damage one with say a 20hz tone.
Music is my priority over movies, and average ported enclosures work fine for me, but if one truly wants the lowest bass you'll want either a sealed sub, or a ported one with a low tuning frequency, and that won't be your typical Best Buy subs. I should note that I think many put too much thought in ultra low response when it's rarely needed in many cases.
I can attest to the advantages of multiple subs over 1. I use 3 actually, and that in addition to using room correction made a huge difference, and much more so than what exact sub you choose.