If you look on forums etc for people switching to dut they usually say there hairline has taken a hit. I think they are going through a shedding phase and are not giving it enough time, get scared and stop or they notice there hairline going back so switch to dut but by then its to late. That is just my opinion.
Iv been on fin or avodart for about 12 years now. Currently on avodart for the past year and have no plans going back to fin.