I personally prefer to play with the BI executable. Not necessarily however because I deem it the more "intelligent" of the 3 exe's. Rather because of the functions it permits..ie..hording, unit formations/abilities, night battles, religion and such. Some of these functions like swimming units, the AI of course doesn't use very well but I like having more options just the same. Some of these alex.exe has and others not, where as rtw.exe doesn't have most of these but things like night battles can be enabled. As far as an actual difference in "intelligence" between the 3 whether it's campaign and certainly battle field AI goes? The difference IMHO, is negligable at best. Besides the aforementioned differences the only thing of note IMO is that naval invasions are certainly more active with BI and Alex than they are with RTW. However I have not experienced any differences of note in naval activity between Alex and BI.