I changed from AVODART to PROSCAR in September 2008, 3-months AFTER I completed the intermittent TAB in July 2008. I used AVODART throughout the 1-year on TAB.
There was really no very good reason that I'm aware of for the switch except (a) I know PROSCAR has been around longer so I hope the long term effects are better known, (b) I happen to know someone aged about 85 who's been on PROSCAR for years without any apparent problem, (c) my night time urination remained at about 2 times a night on AVODART, and I wondered if PROSCAR would work better (it hasn't yet), (d) generic PROSCAR is slightly cheaper than generic AVODART on Alldaychemist.com, (e) most of the men on the Leibowitz-Tucker study used PROSCAR, and (f) my oncologist (Dr Tucker) had no objection when I suggested the change to him.
My testosterone level is very low 3-months after TAB which probably accounts for the low PSA of 0.01. I will check the PSA & Testosterone again in January 2009 and compare the results with the Leibowitz-Tucker study of the first 100 men on TAB. Looks like my PSA/Testosterone may be below the rising curve of this study, which is fine by me, but if the numbers remain low I wonder if I might be able to stop the PROSCAR as well, at least for a time. I don't really want to take drugs if I can avoid it.
Hope this helps.