I don't think there is much of an argument for the CAAD4 with Uletgra. Yeah, sure, the components are superior to that of the CAAD9...they are lighter, shift smoother and may last longer; there is definitely something to be said for longevity. I'd pay closer attention to the framesets, however.
There are many similarities between the CAAD4 and CAAD9, but long story short is the CAAD9 is here to take the place of the dated CAAD4. Both frames are constructed of high quality materials, by quite possibly the best aluminum frame builder on the planet, featuring current trends in competitive road geometry. Where they differ is in ride quality and stiffness; the CAAD9 has generations of refinement to make it a more pure-bred performer than the likes of the CAAD4. The CAAD9 features more aggressively engineered seat stays for improved ride quality; CAAD4 had more conventional seat stays, offering a ride like what one would expect of an aluminum frame. Furthermore, the CAAD9 has increased frontal and bottom bracket stiffness over the CAAD4; the added stiffness will do nothing but help you go faster and ride more stable and confidently as you do it.
Parts are just parts; they are easily changeable and upgradeable. Your frame, however offers much of the performance and character your bike will take on; I'd argue this is more important. Both will be great bikes, but I'd say the CAAD9 is superior. Why wouldn't you want a faster, better handling and smoother ride?