First of all, these two industries have their own merits, the focus is to find the right one for you and what you are good at. For these two professions there are some comprehensive analysis, you can refer to the next, I hope to help you.

UI design is the Internet industry, interior design is the building decoration industry, both pay attention to the visual aesthetics and software operation, but UI design is more focused on the user's experience in browsing the web page, cell phone end, while the interior is more inclined to the decoration of the building structure with the need for a more clearly oriented professional skills, relatively speaking, the need for a wider range of knowledge.

Of course, the core is still in the personal hobby! Do what you want to do, do what you want to do.