if you wieght the pro's and con's to the two fluids its still a tuff choice between the two.
Pro's to the type f, firmer shifts, clutches will last longer with type f and i am told f is excellent against heat. con's to the type f, it lacks the lubricating properties for the overdrive unit, the additives in it die quicker then in the dexronIII and my builder advised against using it.
Prp's to the dexronIII, it is what my builder reccomends using, it does have the lubricating properties needed for the overdrive and the additives last longer meaning the fluid will last a longer, Con's to the dexronIII it has friction modifyers in it, it will cause transmission to shift softer then type f therefore wearing clutches out faster.
so you see after wieghing the pro's and con's its still a tuff choice between the two.