Building a region for SineSpace is easy at first, but can get complicated quickly. There is a lot to learn, and as you add items the filesize of your region quickly starts to expand. Learning to use substances with SineSpace is a great way to keep your region size under control, and is definitely worth your time.
Your regions are limited by their filesize in SineSpace. The biggest contributor to the size of a region is your texture bitmaps. Unlike bitmaps, a ‘substance’ is a very small file. It contains the information needed to render a material. Unity uses it to render the textures when people visit your region. Therefore your region is smaller and downloads more quickly. Smaller regions also means more room for furniture and decor (stuff like this holiday tree – you can never have enough room for that).