IMO there might be a better daily driver that can do autocross/track work than a MK7 GTI out there, but I don't know what it is.
I wouldn't even consider anything pre-15 GTI or the Audi mentioned (which has the older EA888.2 motor, that have all kinds of stupid and expensive problems).
The main issues the EA888.3 has are water pump and thermostats (which are under an extended warranty coverage up to I think 80k mi, Google it). There will be other problems that pop up not on every car, but here and there. Direct injectors failing at higher mileage, etc. PCV valve failure is semi-common, I've been experimenting with a MK8 PCV retrofit (which can be done <$200 or ~$300 depending on if doing the "basic" or "full" retrofit - the MK8 has a wildly effective design that utilizes a Venturi to aid in maintaining vacuum on the crankcase at all times) which works well and has significant design changes even if the Venturi is not utilized.
https://www.datadrivenmqb.com/drivetrain/pcvtechtalk
A 2017 Sport is what you want. It has the HID headlights (which are amazing), no sunroof (which should be avoided at all costs), plus the Performance Pack standard.
The only reason these cars might have problems overheating on track is how they're modified. We found out that all of the companies selling oil coolers for this car tell you to put them in the WRONG spot. Directly in front of the "cold" side of the intercooler. This causes IATs to skyrocket, heats up the coolant (so people buy a $500 aftermarket CSF radiator which actually doesn't do anything helpful unless you induce your own problems via an oil cooler), and causes the car to pull a ton of timing which adds even more heat in the process.
You can read about some of our testing on a buddy's car here:
https://www.datadrivenmqb.com/drivetrain/oil-cooler-location-and-ducting
There is also a bunch of cooling data from a variety of sample cars here:
https://www.datadrivenmqb.com/drivetrain/coolingdata
Main takeaways:
- IS20 (GTI stock turbo) is WAY easier to keep cool than IS38 (Golf R stock turbo).
- Any of the sub $1000 FMICs suck on track compared to any of the stock location ICs
- How hot everything gets is directly linked to how fast you're driving it on track. Unless you're actually legitimately fast you won't have a problem.
- Aftermarket intercooler + stock tune is the best bet if temps/reliability are your concerns.
- 270F oil temps are fine. 20+ days on my car on track in the last 20k and 2 years with no issues. The people who add oil coolers (see above) are the ones who end up with limp mode problems.
- DSG cars will run a tad bit cooler on track all else being equal. The data might skew this a bit, because it happens to be most of the 6MT cars are either balls out dedicated track cars, OR they're being driven in 100F heat in the Texas.
These things are also a ton of fun to autocross, and actually pretty competitive in both GS and STH if you go that way.
https://www.datadrivenmqb.com/tripreports/tsccax3
Sorry for all the links, but that's part of why I made the website: I end up talking about this crap so much it is easier to just reference there at this point.