Hello,
The larger room will benefit greatly by allowing you more flexibility to pull your speakers farther out from the back wall if needed. If they do well with minimum distance from the back wall, the larger room allows the listener more flexibility as to distance from the speakers and getting the audio gear (most likely along a side wall) farther away from the speakers. My basement room (13.5' x 18.5') is very close to your large dimensions and that extra length beyond 16' helps a lot in the ways I described above.
John
The larger room will benefit greatly by allowing you more flexibility to pull your speakers farther out from the back wall if needed. If they do well with minimum distance from the back wall, the larger room allows the listener more flexibility as to distance from the speakers and getting the audio gear (most likely along a side wall) farther away from the speakers. My basement room (13.5' x 18.5') is very close to your large dimensions and that extra length beyond 16' helps a lot in the ways I described above.
John