I'm definitely not saying BR doesn't have its advantages - two of my most recent designs are BR, but before developing them, I had found that the audibility of this delay distortion to me at least is much less when the port tuning is well below 40 hz (they were tuned to 22 hz and 32 hz), and it also helps to have the amplitude response tapered down a few db at the BR tuning to further emulate a lower cutoff slope. But I plan to make my next speaker as a closed box which will have significantly less group delay near its cutoff than a BR with a similar cutoff frequency would. Lowered in band group delay is also supposed to be an advantage of high quality horn bass.