I'm not seeing any difference in weed control betweend drilled and 30" after three years of using both.  This year we have some 30" beans that were planted late and all they've had for weed control is one pass with 40 oz of glysophate a few days after they were planted and they are still clean now. 

Most of our beans had a pre-plant chemical down on them and it was a waste of money, the stuff that got sprayed in May was all washed away by 20" of rain in June and stuff sprayed the first week of July didn't have enough rain to keep it activated so it didn't do any good either.  The other option I see is Liberty beans but changing a bunch of beans to Liberty beans just means that in 5 years we will have Liberty resistant waterhemp so that is nothing more than a bandaid.  This summer I cultivated 30 acres of conventional beans where 12 oz of Cobra stunted the beans more than it did the waterhemp.  I don't like the idea of cultivating beans but before long I'm afraid it's going to become a fact of life.