Here's an interesting article on 'The Best microSD Card' (see http://thewirecutter.com/reviews/best-microsd-card).
It's interesting because it includes:
- testing results from running CrystalDiskMark on leading quality branded cards
- good background information and additional useful material
- my favourite cards were excluded due to being too expensive and faster than most people need
In addressing the last point to afford the fastest I reduce the storage. So I currently use 16GB SanDisk Extreme PRO and 32GB Samsung PRO.
However with such comprehensive test data any future purchases will definitely be well-informed.