Tamiya hands down. The SLR is also quite nice.
With Revell, plan on at least getting replacement wheels and tires from Plamoz. The stock ones are a joke and there are multiple cases of them shipping wrong tires.
While the Revell SLS is older than the AMG GT, it is far better in detail and quality.
For the SLS Fujimi also makes one. Here is a comparison:
http://modelcarshirobom.syanari.com/...omparison.html
The curbside one is Fujimi.