For the same recording capacity, the prices of memory cards can fly off quite easily, in the sense that what will make the difference is the speed of transfer.
The speed of playback will affect the speed of copying to your computer. In other words, it’s important only if you do not want to wait too long. It is not indicated on the map.
As for the speed of writing, it is necessary to record your photos more or less quickly from your camera to the memory card. This is an important criterion if you work in RAW, because these files are heavy and require a high transfer speed. It will therefore be necessary to choose a fast memory card.
The write speed is also to be taken into account if you use the burst mode or if you record videos in high definition. The indicator (example 30MB / sec, 45MB / sec, 90MB / sec) displayed on the map is maximum data.
Another indicator expressed in X guarantees the maximum flow rate at which the card can support. To know the equivalence in transfer speed, it is enough to make a small calculation.
The speed indicator X 0.15 = the transfer rate