A 90" long port will probably have to be bent several times to fit in your enclosure, leading to compression issues, which are already a problem with slot ports. Even if you could somehow do a straight shot 90", you'd still be looking at a port resonance at 75Hz, which is right in the driver's passband and would be audible as a sluggishness around that frequency. For these reasons alone, I'd avoid the ported option (which is why I think CSS only recommends using passive radiators with them), but when you add in the simplicity of the build and the fact that 2 subs sealed will have as much or more output capability as a single ported, I think the 2 sealed option wins in a landslide.