I'll give you my "professional opinion"
Nissan: I like the shot for what you're trying to do. If I was doing the shoot for a magazine this would be one of the shots I took and would use. Great use of the background and putting the car where it needs to be.
Could you have gone a bit tighter, totally could have but it did not wreck the picture one bit.
Recommendation: When I do shots like this I will have almost exactly like this, then take a few others with the car tighter in the frame so I wouldn't' have to crop it. It's always nice to have those extra shots.
VW shot: Again not a bad picture at all for what you're trying to do. Good use of the background and framing.
What I don't like is the curb, it's just a little distracting and that's the only real negative thing I have to say.
Recommendation: Always be wary of the background and what's in the shot. I still struggle with this at times and have jacked up shots because of this.
Overall, based on the shots I see you post online I would hire you for my magazine to do a photo shoot if I needed someone. Your work shows good composure and an understanding of how to make the car "talk".
Now, if you really want to learn to be a car photo gangster work on those interior, under the hood, and abstract detail shots. Those are some of the toughest to get but will take a shoot to the next level.