Assetto Corsa is a great game but lacking any weather or light effects. Competizione lacks tracks and different car types.
I honestly prefer Dirt Rally 2.
Competizione from what I can see have a content roadmap as far as 2021, mostly GT but I'm fine with that as long as the Career is any good. Haven't had chance to look into either yet, following the news currently but DiRT 2 will be a must.