It will matter if you capture high resolution videos or pictures(mainly) , or if you have all of your apps on your sd( Neglectable). Just think about it like a pc every time you access the slow hard drive it bottle neck your computer. But everytime you use your ssd it goes fast. So if you are just using it to put music on and books you don't need a super fast one. If you want to use it for videos and high performance tasks you need something with high transfer rate. You can go with lexar in my books pny and lexar are on the same level (experience).