While both will work, the iPad Mini 4 is faster, brighter, and lighter. A 16GB iPad Mini will be good enough if you're not going to install a bunch of other apps on it.
If you have the funds to purchase a brand new one then I would wait. There should be a new Mini out early next year. Ok, no one knows the exact date but I believe that Samsung will be bringing out the S3 in February/March so it will probably be no later than that. I personally will probably go for the S3 (at this stage anyway) but then I prefer android even though I use both....