Online: Depending on the community you're in. I had fantastic Endurance races in rF2. The only games that supports driver changes (except LFS) are rF2 and iRacing. rF2 is still in "Beta"
In shorter races without driver changes? rF2, AC and pCars and not in iRacing. But that's only my experience and preference.
Career: Don't really care about it. And that's why iRacing isn't my cup of tea. Don't have time to grind. The physics is not nearly as good as AC, rF2 or even pCars. Most racecars are
easy to drive in real life, especially GT3, GT4, up to a certain level. It's when you are on the edge and trying to get the maximum out of your car it get hairy, that last 1-5% is really hard. AC and pCars best simulate that aspect. But then I always run with the same ABS or TC as the cars use in real life.
Final thoughts:
The poll should be a multi choice.
I can pick a car in AC and just drive around Nords for relaxation. pCars makes me want to go to LeMans and revel in the atmosphere and the visuals with 39 other cars. Thing is, that no sim so far has it all... at least for my favorite type of racing, endurance.
I want pCars visuals, AC FFB (I know that it has some canned effect but it also talks the best to me),
rF2/iracing driver changes, Nascar2003 recovery vehicle, GT6/AC tracks and pCars for cars (LMP1,LMP2,GT3 and GT4).
All that combined with a engineering/team boss module for managing the team/race/pistops.