I don't think those CEA-2010 numbers are comparable, so I wouldn't go by them. The bottom line is, these subs will probably have comparable output at around 20 Hz, with the ULS having an advantage from 30 Hz to 50 Hz or so.
Either one of these subs will be in over its head in a room of 4,500 cubic feet. If I could only pick one between them, I would get the ULS without hesitation, however, you might think about adding more subs down the road, in which case they should be matching, so the PB-1000 might be a better choice for a multi-sub setup.