I heard both subs with and without speakers playing, not in my system though.
I heard the sub only playing music with the speakers turned off, not playing HT... no comparison, the SVS plays like an actual subwoofer and goes very deep, the speedwoofer not so much.
As for playing with speakers, I did not hear them with OB speakers but with Salk HT1-TL and with Emotiva T0+...and again no comparison. The speedwoofer didn't blend nearly as easily, probably because of no parametric option and definitely didn't have the authority.
Yes, the SVS cost quite a bit more, but it sounds quite a bit better and I think the parametric is worth it in order to give you the maximum placement flexibility with the ability to still get good sound.
I had the Spatial M3 Sapphires...and yes, they are easier to place in a room with respect to bass than a box speaker, but if you crave the slam of a box speaker, then you will need a sub that goes low to help out on the bottom end. In my case, I used a Power Sound Audio S1500, 15" sealed....and felt very fortunate that I was able to get it to blend well without the parametric help.
