I do not have personal experience using an iPad Mini, but I can offer a few thoughts:
First, the iPad already has a shortage of screen real estate. There's not a lot of room for menus, tools, let alone your art. I can only imagine that it is even more cramped on an iPad Mini.
Second, iPad styluses tend to have wide tips and are not as accurate as normal pens. Drawing with one on a small screen is only going to amplify how "fat" the stylus feels. You may be in for a frustrating experience.
Also note that the physical size may change how the sensors and sensitivity works between the iPad and the iPad Mini. Because of this, you may run into stylus problems, such as the tip being less sensitive or less accurate. Some of the fancier styluses that require electrical signals or feedback may not work at all.
Other than that, I don't think there is much technical downside between the iPad models. All the apps should work the same. Most styluses should work just fine. I know there are artists out there that are using iPad Minis for making art with no trouble. I think the decision will ultimately come down to your own personal preference, and what stylus you like to use and if it functions properly with the Mini. Check the stylus manufacturer's documentation about the iPad Mini, and if you can, try to test out a Mini in person before committing to a purchase.