Using the argument bs with dd when backuping sd card

Question

I've seen this question on how to backup a SD-card. It's the same solution I would come up myself, that is basically dd if=/dev/blabla of=/home/user/some_file.img. But my question is if using the argument bs=1M makes any difference. It does when I'm writing to the card so I suppose it does when I'm reading from it. Are my assumption correct? In the question I referred to earlier it differs in different answers.

Answer 1

From Wikipedia:

A block is a unit measuring the number of bytes that are read, written, or converted at one time.

...

For some uses of the dd command, block size may have an effect on performance. For example, when recovering data from a hard disk, a small block size will generally cause the most bytes to be recovered. For greater speed during copy operations, a larger block size may be used. When dd is used for network transfers, the block size may have an impact on packet size, depending on the network protocol used.