I would definitely recommend the Retina. I have had both, and don't mind the difference in screen quality all that much myself, but the performance is a lot better. However, some people have been experiencing issues with low speaker volume on the Retina, I personally don't notice them myself, but if you play music through the external speakers then you might want to look out for that. As for reading, if you mean reading webpages, I would definitely go for the Retina, not just because of the screen but also how many tabs it can open compared to the mini. (Also, you by getting the original mini these days I believe the price difference is only about $50 now, not $100 like the pre-mini 3 days)
In terms of support, don't expect the mini to get support past iOS 8, although it certainly is possible it gets iOS 9. Performance has taken a significant hit for me with iOS 8, it just doesn't feel as smooth with iOS 7. In the end the best solution would probably be to check them both out in store, or even see if you could borrow somebody else's iPad and give that a shot.