Fuzion is a high end wax that works well with both dark and light vehicles. You have both dark and light cars so it seems to be a good option. It also has better durability than terrific high end beauty waxes like Souveran that last a couple of weeks. Fuzion is great as both a beauty and a higher end daily driver wax if that makes sense. MaxWax is sometimes referred to as a poor man's Fuzion, so it could be another great option.
I'm not really sure if a hard vs soft wax is the right differentiation. I personally want something that lasts a couple of months between waxing. I want something with a look that is more deep with a glow versus a harder, mirror reflection. It's a personal value and you may perfer something different.
If you list out the characteristics that are important to you, I'm sure you will get a shorter list of options.
