I have not used the wireless function on the ULS-15s. My subs are set up stereo fashion next to my mains. Wireless...it's nice to have the option, I just haven't needed it. And yes, it would make finding the right location easier. The only possible downside is interference with cordless phones or anything else that might use the same frequency as the wireless antennae. There are several channel options to combat this however.
You will not give up anything using the ULS-15 vs. a ported sub for movies. These things offer bombastic amounts of bass. My pair are somewhat overkill, but at the time I wanted more headroom than a pair of 12s would give in my room. Large volume, large vaulted ceiling, open floor plan...all that bad stuff.
That said, if sound quality is your main objective, I would still lean towards the SB13+ if your room is on the medium to small size. The ULS could be considered overkill, and while it goes a lot deeper and louder than my SB12 pair did, they required the employment of a sub EQ to tame them. My room had some awful room gain. The SVS subs weren't as chest thumping deep, but in my opinion offered up better sound quality for music. I'd expect the SB13 Ultra to provide better SPL output than the SB12+...maybe as much as the ULS-15. But I don't know for sure.
As a home theater sub, the ULS is flawless, and a great value in my opinion. For 2-channel audio, I'd likely seek out another SVS sealed unit...or two. :-)