Since mendes9 mentions that the two seemed to differ most at the higher frequencies, and Cadboy mentions a similar experience going from a 12" sub to a 10" sub, could some of the difference be due to the fact that a 12" driver (such as the one used in the LFM-1) is going to drop off more rapidly at the higher frequencies than a 10" driver (such as the ones used in the STF-2 and UFW-10)? I'm not sure how the four subs mentioned in this thread compare at higher frequencies, so I may be off target with this thought.

Also, I always suggest tinkering a bit with the bass management when changing subs - I was able to push the crossover up from 40Hz to 60Hz when I got the LFM-1 and still have it blend smoothly with my mains on two-channel material, and changes like that can yield some interesting results sometimes.