There is surprising variation in the performance of SD cards. They are not all created equal and the differences can impact the running of your Raspberry Pi, no matter which model. [Jeff Geerling] wondered exactly how different cards would affect system performance. He ran a number of tests on cards ranging from cheap no-names to well-known brand names. The no-name cards fared pretty badly but even among the brand names there is considerable variation.

Raspberry Pi microSD card performance comparison – 2015
http://www.midwesternmac.com/blogs/jeff-geerling/raspberry-pi-microsd-card

Raspberry Pi offers custom-made, mass-produced boards
http://www.engadget.com/2015/10/27/raspberry-pi-customization-service/

It’s one thing to buy a Raspberry Pi for your own tinkering, but it’s another when you need to buy a lot of them for your company — you aren’t going to tweak thousands of boards by hand. Thankfully, you don’t have to. Raspberry Pi is teaming up with Element14 on a customization service that lets organizations order 3,000 or more specially-made boards at once. You can use the service to add or remove connections, rejigger the layout and otherwise get the exact mini computer you want. This is helpful if you’re going to sell a Raspberry Pi-powered device (particularly important for appliances and other connected gadgets)