We tested four modern laptops’ SD card readers and found huge performance differences.

For content creators, a laptop with a built-in SD card reader is a preferred feature. Some users go so far as to consider laptops only if they have a reader.

One mistake with that choice is it assumes all SD card slots are created equal. Our tests clearly show they’re not. It’s also difficult to know how fast the SD card reader in your laptop is. If SD card speed really matters to you, the best way to get what you want is to buy an external reader whose specs are clearly designated. 
…
Read full post here:
https://www.pcworld.com/article/3570415/why-your-laptops-sd-card-reader-might-be-terrible.html