Depends on what you class as professional, but i have 80 gold and i use roof cam. roof is the same as bumper but it gives a better view of whats ahead IMHO.
bumper cam gives the best sense of speed and physics. you lose most of the braking and acceleration suspension effects with the hoodcam... if the bumpercam was a bit higher it would be better - like driver's-eye-level - but I'll manage with how it is for now.
I'd been playing using the bumper cam, but it still didn't feel quite real to me because in real life, you still see the hood of your car. I've since switched to the roof cam and it seem like a whole new game to me now. It seems more real I guess, because even though my eyes are on the racing line I want to take, I can now see the hood in my peripheral vision, if that makes sense.
I'll take either the roof cam or the bumper cam. In GT3 and most other racing games I use the bumper cam exclusively. It puts you right on the racing line like your leading the car rather than the car leading you (3rd person).
However there's only two drawbacks. Sometimes you can't see a curve in the track until your're right on top of it. La Sarthe does this to me with the last two chicane like corners before the start finish.
The second obvious drawback is that you never see the car. For all of GT3 i felt like I was just really good at piloting a speedo and tach around various tracks. I didn't need car. My guages were fast enough.
So in GT4 I'm lovin' the roof view. I at least get to see a near sweeping view over the hood so I always actually feel like I'm driving a car.
Now if I could only figure out how to turn the speedo and tach off...
I put in probably 1000 hours in GT3 with the bumper cam view. Now I can't get comfortable with any other. I tried the roof view but it makes it seem like you are driving a Mac truck. All the other cars seem so small and below you...
In car view for me... 3rd person view doesn't make me feel like I am driving, makes me less precise too because I can't feel the weight shift delay that way and always anticipate too late.
I prefer bumper cam. I have tried the incar seat,but not fond of it. The view behind the car where you see the whole car,is the pits IMO. It screws me up when I see the car drifting in the corners on this view,I always tend to oversteer.
I usually use the "driver's seat" view to see the track ahead better than with the bumper cam. But if it's a tiny car like the G4 or even M Coupe, i like to have the outside view to control wheel spin better.
personally i like the in car view because it's more of a realistic feeling...and i also think the 3rd person view is like controling a remote control car...the hood view is alright but on some cars its a veiwing ugly vew ...
I used to drive in GT1/GT3 in the first person view. In GT4 I drive with the bonnet view. I can switch between that and first person view pretty easily. I never drive with third person view but I expect I could get used to that easily enough. It makes little difference really.
I still think bonnet cam is easier, because it is easier to see where the nose of the car is pointing. If you like to drive a car 'on the nose', like I do, it's ideal.
I like the third-person view. If I drive the bumper view, I don't know what the car is doing. I haven't really tried to roof cam. The third person view is the only way that works for me.