No doubt that there were different situations and had units with different organic capabilities. However, having worked for a few weeks alongside 4ID and for a few weeks alongside 101, there was a world of difference, and much further beyond what just the different situations would create.
It was probably only a flash in the pan, but I had an opportunity to experience the 4th ID firsthand in mid-April, during the RIP between their elements moving north to Tikrit and TF Tripoli.

We were coiled up north of Samarra, basking in the joy of finally receiving packages and mail, when OH-58s and Apaches appeared over the long line of HETs that were dragging gear north to Tikrit. It was a little bit uncomfortable to watch an Apache circling the battalion TAA, tracking personnel on the ground with the slaved chain gun. Definitely a WTFO moment. It didn't stop there though, and within 15 minutes of the air troop's arrival, we had to call in our patrols because the Apaches began firing rockets, guns, and Hellfires at hell knows what across the highway, only a klick or so away. Needless to say, we were not impressed.