Interesting topic.
In 2010 game I just could not drive cockpit. (Xbox no mods R Us). Felt like I was too short to see over my hands. Much slower than in T-Cam. One guy in our league was a real purist and only drove cockpit (and no assists even though permitted).
Once 2011 came out I found cockpit a huge improvement. On my first test session I did lap time comparisons and to my joy I was quicker in Cockpit. I was so happy to now be able to use it.
Very happy in cockpit view, totally used to it, getting more feel of car attitude. When I watch replays and switch camera views it just illustrates to me that in Cockpit (in my view) you are in and driving the car, T-Cam you are watching it.
One more thing about "Racing line" assist. I leant on this for a couple of career seasons in 2010 game. Once you turn it off the game goes up a level. You find real braking markers and start driving a track rather than following a line. I got faster very quickly once switched off as I started to feel the track.
I recommend dropping this as soon as poss, maybe just use to learn a new track-hey maybe I will use it in India and Nurburgring for 10 laps each.
Every assist I drop lets me enjoy the racing more.