I put myself in the "other" category. Ever since GT1 through GT4 I have been a Time Trialler, cos back then the AI was (and still is) stupid, and there was no network racing. In all my years I would guess I've done hundreds of thousands (millions?) of laps around Trial Mountain, Deep Forest Raceway, Grand Valley, Autumn Ring & Mini, SSR11 (ver.1), Apricot Hill, etc...combined of course.
Now with GT5, the common tracks I find have a vastly different feel about them, and time trialling isnt what it used to be. The corners feel tighter, cars feel more understeer-ish, less responsive, and overall it just isnt as fun. I haven't gone back to compare lap times around any circuits, but a couple of numbers that have stuck in my head over the years involves the Mitsubishi FTO LM edition (now stupid "Super Touring"), and Autumn Ring Mini. Back then it used to be (I think) a 900hp mini monster, and would pull out roughly a 27.3 sec lap. Before you say anything, I know its a fantasy car, and fantasy track, but hey, Its a game.
Nowdays we get 495hp, and this will net roughly a 33.5 sec lap after 10mins worth of setting up, albeit on about my 4th day playing GT5. I know the physics are vastly superior nowdays, and I can understand that playing a role in the slower lap time. The raw power of the old car compared to the new might account for 2 or 3 seconds (lots of turning, balancing the car, little in the way of full bikkies).
To me, the whole idea of these fantasy tracks is that they are fun, and something of a challenge, and through GT1-4 things felt quite similar. Now this track feels tighter and slower, so theres no direct correlation to anything that has come before it, and theres now much less fun involved in TT'ing the fantasy tracks.
So I've had to find some other way to enjoy my time in this game.
Online seems to be where Im spending most of my time, I've made a good amount of 'friends' who are clean, fast drivers, and I usually get 20+ races done each day/night. Some days I wont have any cars in my "Favourites" list that are on par with the room regulations, and Im happy to finish mid-field after a bit of a battle off the line. Other days are too easy, where no-one else has cars as "good" as mine.
But then theres the best days, where up to 6 of us all have different cars, different peak power, min weight, etc, but ends up making for really close racing where we are within 1 sec first to last for 90% of the race.
So in that sense Im a Racer, with a bit of casual on the side.
Then on the other hand, I started thinking about how much time PD 'may' have spent programming each car for their respective handling characteristics. So I decided to start buying cars I hold in high regards, driving and getting a feel for them as stock, then tuning them to a reasonable level, leaving as many standard things as I can, but most importantly Keeping The Same Feel Of The Car. I usually end up on Racing Soft tyres, and always buy Race Suspension. Take a limited amount of power upgrades (dont want to spoil the standard gearbox), whatever exhaust gives the car a nice note (sometimes stock is best!), and trim the weight a bit if I dont think it will ruin the car.
Doing this is starting to bring back the "fun" I remember of earlier GT titles. Now you might say, why not just drive the car stock if Im aiming for the same handling?
I dont know, something about going faster, in the same style "does it" for me.
This however is not for time trial purposes, although I am making the car faster, just doing it for the sake of the challenge it provides, and the enjoyment of the different handling dynamics of various cars. Perhaps its bringing back a similar level of "response" feel previous GT titles used to have.
And in that way, im a bit of a soloist (Loner - I know

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Since there is no "All of the above" poll option, I guess im thrown in with the weirdos.
Now if you have bothered to read this far (thanks), my favourite cars to tune MY way so far are the 430 Scuderia, GTR SpecV, Lotus Esprit (all versions) and both Spec C WRX's. And after doing a one make race in a Shelby Cobra a few nights ago, I think that may be next on my list (best feel of acceleration/speed I have had from any car yet, X1, F2007 included)