I personally select the middle range model because I know that if I choose the top version I will crash it in no time, and if I choose the worst model I will find it too slow.
I normally either go with the base model, by just double clicking the image, or I look for one that is a dragster, or in a color I like. I normally don't change up the colors of the cars from default, so a good color is something that means a lot at first glance. I also check to see how high the Performance Class is.
I choose the default model, followed by the highest end model, followed by any custom, race, rally, and / or drag variants, followed by the base model.