I've had two of these cars and some other cars too. These are just my opinions.
808, car is in my opinion under rated. Took a couple days of testing and found I don't like the car unless the front camber links are in the top hole. Doesn't seem to like a rough track as much as some of the other cars. Car is tough as nails and steers pretty good.
MBX6, car is usually setup what I feel is good. Never feel it's perfect. But even when it's setup bad... it's not that bad. Car is always easy to drive and I always feel like I could push it more. Relatively reliable and easy to maintain. Great car.
RC8, turns on a dime. Love a car that has tons of steering and the RC8 is that car. I find myself on my lid more with the RC8 than the other cars. It's fast but not Mugen/Xray quality if your into that stuff. Small tight track it's my favorite car. Not sure if they've got their fuel tanks figured out, previous versions seemed to have some issues.
8 2.0, well I like a car that turns on a dime. That isn't this car. I think losi makes a fortune on selling hopups that should come stock on some of their products. Car is very stable though and jumps nice and predictable. I've had good luck with reliability. Wear and tear like the front drive shaft pins seem to wear quicker than others. Big track it's a good stable car. Small track I just can't get it to turn as well as the other cars. And yes I spent what I think is way to much on the inclined spindles. Overall good car though.
As a mid pack sportsman driver those are just my feelings on those cars.