To offer my 2 cents since it's a topic I had some interest in:
The LMS-U does have an edge in low end output per DB, but there are some factors to consider:
1. It's in a larger cabinet than the Funk driver, which improves low end sensitivity and reduces distortion.
2. We don't know the voltage needed to drive the LMS-U to max clean output in the burst testing, but we do know that it took 130V to push it to ~108dB at 20Hz, which is a bit over 4kW into 4 ohms.
To get a different picture, you might also look at Ilkka's measurements of the LMS-U in a 100L cabinet, effectively the old version of the FW18.0:
http://www.hometheatershack.com/forums/subwoofer-tests-archived/8155-diy-tc-sounds-lms-5400-18-sealed-100l.html
Even there, its being driven by 3.6kW of amplification vs 2.4kW, which theoretically represents a further 1.7dB difference. Still for Nathan's purposes it starts to become clear why the TSAD is preferred: in the 18.0's cabinet and with a 2.4kW amp, the LMS's low end advantage largely evaporates, while the TSAD still has a useful advantage in upper end sensitivity/output.