what's the difference between Ultra and Extreme and Class 10 and Class U-3
If I wanted to do lots of HD video recordings is it better to get the extreme or the Ultra and is the Class 10 or the Class U-3 a better choice?
It is all about data transfer rates. You need to find the minimum required data transfer rate for the HD device you are using, and that will determine which card to go with. A rule of thumb, the faster the data transfer rate, the more expensive the card is. So make sure you don't go overboard and spend too much money on a card that is faster than you need.
SanDisk - Ultra PLUS 16GB microSDHC UHS-I Memory Card
(703)
SanDisk - Extreme PLUS 16GB microSDHC UHS-I Memory Card
(694)
Samsung - EVO+ 32GB microSDXC UHS-I Memory Card
(5,928)