The conventional analysis suggests that if you convert to Roth or withdraw from TIRA at the same tax rate, the Roth is ahead if you pay the conversion taxes from outside sources and the Roth/TIRA are equal if you pay conversion taxes from the TIRA.
That suggests that if you convert at 25% or withdraw at 25% , the deciding factor might be where you pay the conversion tax from. Some other factors: if tax rates go up in future, then it might be beneficial to convert to convert more. A complicating factor: if you have significant qualified dividends/LTCG, converting more into the 25% bracket might actually result in a 30% effective rate now (15% on the extra conversion if still in the 15% bracket for ordinary income + 15% on QDIV/LTCG displaced into the 25% bracket).
I was playing with H&R Block Taxcut and I saw your point regarding the 30% tax rate (more like 33%). Worse, when I tried increasing my coversion from 20K to 25K, the tax increased from 6094 to 8295 - a 44% tax rate. THis is when AMT kicked in. Hard to comprehend paying 44% now to avoid paying 25% later. I just might limit my conversion to 20K.