When I tried 475PB it in a SEOS15 setup with XO below 1400Hz I experienced an increasingly stronger sibilant distortion as the XO-frequency was lowered. I simply could not use it with the SEOS15. With DE250 I have never experienced this behaviour.
For the two setups I used linear phase FIR filter with steep crossover slopes.
At the time of the test I had not the possibility of doing proper measurements but I found an interesting test done on various 1" drivers in a 500Hz JMLC profiled horn. These measurements shows that HD increases below 1,3kHz on the 475PB. Without being shure, I have suspected this increase in distortion below 1300Hz and triggering of eventually higher order modes to cause the problems.
Due to my experimence I have therefore been very reluctant to recommend the 475PB unless crossed over 1500Hz+... IMO it then sounds better than the DE250.
However, if you (or others) have very good results with the 475PB using it in the sub 1500Hz region, it would definitely be very interesting to find out the root cause of the problems I experienced.