I am an apple fan if you can't tell, but I own a little bit of everything.
iPads are great, screen is very responsive, movies are crystal clear, works seamlessly with my iPhone, iMac, and MacBook. But you pay for it. They are not cheap. Resale value is great though too.
My kindle fire hd is awesome for reading books, recipe books, movies on amazon prime. The screen is not very precise, slow response. Opening web pages seems very slow. Battery life is not good if using wifi. If just reading, it's great. They are not expensive.
Wife has a dell tablet for work. Have not heard her really complain about it, but it's set up to run specific programs for work.
If I had to choose one it would be the iPad, but I will say for the price, the kindle is great.