I think it depends on the car you are getting
I had a SMAX and the tint was horrible for night reversing (as mentioned on this post) and my sister in law complained it was gloomy. But in my BMW it is perfect, barely notice it from the inside and it is very dark form the outside.
Mmmm, ok so I’ll come clean, it’s an Audi A6 (but I don’t wear cufflinks, have an ipad or ride an Orange 5 before anyone asks)
I think Audi tint with 20% from what I have read which is quite dark, the one I sat in wasn’t too bad looking directly out of the window, it was more the general gloom pervading the inside of the back of the cabin I thought might be a bit depressing for the kids.