I've had aquariums that come with everything (CoralVue T32 system including tank, sump, stand, plumbing), and I also have a Planet custom with components and plumbing I selected myself. The tradeoff is accepting what someone else has decided for a component list versus getting exactly what you want. If you are picky the extra money for a non-packaged system can be worth it, but if you are more interested in convenience, startup time, and saving money then the package can be a better deal. Of course some of the packages have poor quality components or various other issues so it's always good to look for reviews and experiences with whatever you get. I would add that with a package you are likely getting a system from China and they often have plumbing that is metric so finding parts or making modifications can be challenging. With Planet you are getting American made up the road in Dallas.