driver decision
Hey guys. I'm in the thick of design right now and there's a pretty smoking deal available on both a TC2000 DVC 15" and an LMS4000 12". i've been doing some modeling in winISD with both of these drivers. i'm really looking for clean, fast, accurate sound down to 20 Hz (lower would be just fine too of course

)
here's what i'm looking at right now:
the first is for the tc2000 DVC.
i've got it modeled in a 13.9 cu ft. enclosure tuned to 17.3 Hz. dual 6" ported with 32" vent length. butterworth high and low pass filters at 15 Hz and 120 Hz.
the second is the lms 4000
this one i've got set up in a 10.6 cu ft enclosure tuned to 13.4 Hz with dual 4" ports 33 inches long also with butterworth high and low pass filters set to 15 Hz and 120 Hz.
both systems modeled running 1200 watts.
i'm having a hard time understanding how the 12" driver is modeling so much more linearly down to lower frequencies. i'm sure that i'll be happy with either of these options as i've heard nothing but good things about either of them.
is there a reason to go with the 15" rather than the 12"
let me know what you think, thanks.