Well that's really a subjective question. What defines quality of life for a ball python? They eat, live, breed, and thrive in racks just fine. So by those measurements they have a good quality of life.
I think people often project things that we define as being a quality life when it doesn't really apply to ball pythons, and other animals in general.
I like racks for their convenience and the fact that the animals do well. I know others who would prefer a multi unit like yours as they want to have nice elaborate set ups with logs/vines/etc.
So its really a personal decision. If you meet the snakes basice needs, then a rack is just fine, and your snakes will be more than happy in it.