Wheels will always be the benchmark. But Gran Turismo manages to make the controllers pretty damn competitive.
When it comes to the .1% or less of players, basically, the aliens, you are not going to match them with a controller, forget about it. But any less than that, controller users can compete with general top-tier wheel users.
The difference is going to be more noticeable with cars at both ends of the spectrum, the really fast cars and the slow cars that take some getting used to and are very twitchy.
Regardless, the Olympic ESports TT with the GR010 is statistically the hardest to get gold by a considerable margin, it's the only one with less than 1% gold times and it's also the one with the most participants which makes it the most accurate sample:
Hardest TTs to gold by %:
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MY personal hardest was actually the Red Bull X2019 at Road Atlanta... However, this was because back then, the DualSense settings were completely messed up, and the DS4 for some reason was considerably faster than it. This was patched in the update right after though.
The NSX at Nurburgring was hard for lots of reasons... One of which, was Tuning. So you were basically not on equal footing with other players, plus the car was the NSX... Which while a very good drive, it was still a handful and of course... At the Nurburgring with over 170 corners to gain/lose time on.
The Theoretical hardest TT would be something like the Tomahawk X at the Nurburgring. Pray it never comes.
I do one every week as well, usually on a weekend day.
I however stopped trying my hardest for a while now, aside from the really hard ones where I have to actually put some effort to get gold.
If I do like the TT combo, I tend to go the extra mile as well, but still not super into it.
These days I only go for a lap that guarantees me gold by the end of the TT.
I dislike any form of Willow, plus, on a car that doesn't interest me, so I definitely won't sink much time on this one. Unless it turns out to be extremely hard, which I doubt it.