To me this one is pretty clear. Urban armor is the way to go, for either an iPad pro or a surface pro. Urban armor makes really sturdy rubber cases with big corners where the tablet is most vulnerable to damage during a fall. This protects it from a fall and paint, charcoal or pastel dust on an easel. It is also nice to have when you are taking it with you to and from the studio or just out and about using it for any purpose. The studio can be a messy accident prone place and you should protect your digital drawing tablet with a sturdy case. Urban armor cases also include a pen holder which is a plus as it is nice to have somewhere to put your stylus during break between poses. There are other cases, but either they are not sturdy enough or cost a bit more for no good reason. Some people might have a style of case they like better for instance a leather case or maybe a faux sketch book but too me the important thing is functionality. So I recommend urban armor cases.

The one problem is urban armor gear does not make a case for the 15 inch surface book, which is in my opinion the best and biggest slate you can get for drawing. The best case that I found for the 15 inch surface book is the iPearl case. It is still not what I would describe as good protection but it is better than nothing at all.